Association of Polytheist Traditions
The Nature of Humans
Humans evolved  as social animals. This evolution may have been nudged along by various deities, seeking either to improve the overall world, to make the human species happier and more successful, or simply seeking to form relationships with humans and proto-humans, and then to assist those beings and groups with whom they had formed connections. Rig, in particular, is said to have assisted human development, both by manipulating conceptions and teaching one particularly promising human child. 
Human beings are intelligent, capable of thinking before acting, working out long term consequences, and creating and transmitting culture. Some would call this rationality, though that word is now often used to refer strictly to logical calculation, bereft of emotion or intuition. This is a trait we share with deities.
Humans generally have spiritual  cravings of some kind. We are inclined to respond to overtures from deities, to seek them out, to try to connect with them directly, and to include them in our social communities. We seek meaning, and purpose, and to understand what comes before and after mortal life. This is part of our innate wiring, though some have it more strongly than others.
As social beings, humans are always embedded in a social context. We understand ourselves in part through roles and relationships. We are neither happy nor healthy when isolated from other humans, and we try to make up for our isolation by emphasizing what relationships we have, both with distant or remembered humans and with other beings (pets, deities, etc.). To change people's behaviour, the social context must be changed, not just the opinions of individuals. We understand things as "true" or "false" in part based on the reaction of those around us. No matter what interests we may have, we seek to share them with others, get feedback, and even build communities around them.
Because we evolved to live in small bands, we have a kind of built in inconsistency in the way we approach other beings, particularly other humans. On the one hand, it is natural for us to love our fellows, starting with family and spiraling out into our community and beyond. When we see a human in trouble, we want to help them, to share with them, to risk our lives to save theirs. But on the other hand, we also want to compete with them, dominate them, gain a higher status in our band and better access to food and mates. Moreover, both these traits are strongest with those who are closest, socially. Those far away can be seen as little more than part of the environment, to be ignored as if not really human, or feared as dangerous potential rivals.
We are also limited, and to a far greater extent than the gods. We must make generalizations simply to function, rather than look at each situation individually; this leads to prejudice and other problems. We cannot help everyone who needs it. We cannot even pay attention to everyone. We have to ignore some things, and some people. We have to leave some people without assistance, even when we do not see them as dangerous, or rivals.
Corporeal existence has other consequences. Our cognitions are affected by our biochemistry, which is strongly affected by our environment. These reactions are sometimes helpful, when we feel sympathy and kindness, or even justified anger, but sometimes they are very much unhelpful, when we become overwhelmed with unjustified anger, or stress, or depression. We also know ourselves short-lived, and begin losing capacities before we even reach full emotional maturity. We are vulnerable to many things, which we cannot always prevent however hard we try. Thus, we have a tendency to experience our lives as a process of weakening and loss. Yet at the same time, we tend to accumulate good things with age, like knowledge, friends, property, and status, and so can also look on our lives as a process of development and gain. However we look at it, though, we cannot escape the effect of being embodied, however much some have tried.
Humans are not really all that smart, or foresighted. We're good at handling familiar situations, or situations our species or culture has encountered frequently in the past. We are not so good at dealing with new things, or things where a short term good is likely to be followed by a long term loss. We put a lot of effort into teaching our children things like delayed gratification, and avoiding trading short term pleasure for long term distress, but we don't do all that good a job of it, as can be seen by looking at the messes, large and small, that most people manage to make in their lives.
We are also inherently selfish, in the sense that we're pretty much hard wired to take care of ourselves and our close relations first, except in exceptional circumstances.
At the same time, we are inclined to want to be less selfish, less shortsighted, more loving, and more effective. We try to improve ourselves morally, intellectually and materially, and we respect those who do a good job of living, showing foresight, self restraint, kindness, and wisdom. Moreover, it is natural for us to try to think about consequences, to learn, and to plan.
We are thus midway between devils and angels,  having traits of both, in a paradoxical synthesis which is also a never ending tug of war.
There was no fall, and no golden age. Humans have always been this way, with details changing as our environment and culture changes. We probably had many of these traits even before we were human, except that there would have been less cultural transmission, without words, and a far more limited capacity for conscious thought.
The principle of Wyrd, discussed above in the context of deities, applies even more obviously to humans. Acts have consequences. This, combined with human nature, is the source of most of what is wrong with the world, but also of most of what is right. Our actions and choices today follow from what we have done in the past. But the choices we make today will shape the choices we can make in future.
This applies at both an individual and a group level, and even at the level of whole cultures. At a cultural level, for example, it's easier to modify an existing political system than to adopt a completely new one. Adding a few elected councils is likely to work better than going direct from absolute monarchy to representative democracy. It takes time for people to get used to debate and even voting. If you do go direct to an all new system, generally because of a revolution, it generally takes a few tries to finally get it right; meanwhile, there tends to be a succession of revolutions or coups.
Fortunately, when people get something right, it tends to be self perpetuating, at least until conditions change. A solution that works is imitated, and taught to children, and perhaps tinkered with about the edges. It isn't replaced with something new and different, unless it ceases to work. Thus, for example, Europeans and their derivative cultures have mostly figured out how to avoid having wars about religion, after far too many examples of why such wars were good for no one.
Unfortunately, it frequently takes us quite a while to get things right, and we often wind up in pretty bad circumstances while trying to solve a new problem. This results from a combination of shortsightedness and Wyrd. In unfamiliar circumstances, our shortsightedness leads to us fumbling around, trying things that aren't likely to work. These mistakes have consequences, which affect our future options. If we waste resources, or alienate friends, they are gone; we don't get to reload our saved game and try again until we figure things out.
We also frequently improve one thing at the expense of another, which then needs its own cycle of improvement. Thus a workaholic might address his job stress by switching to a less demanding job, only to find he doesn't know what to do with free time. He might then take up a hobby, such as learning to play the trombone, only to find that his enthusiastic practice sessions irritate his neighbours. Meanwhile, his reduced income makes his life difficult in other ways, so he decides to solve both problems by moving to a less expensive home with less demanding neighbours. The only problem is that the new house needs some work, which he must learn to do himself, so as to stay within his budget. Because conditions change frequently, we pretty much never reach a stable state of perfect adaptation to our situation, neither individually nor as cultural groups.