D&D rules, by themselves, though, don't help you understand much of anything else.

• The influence of Charisma on social discourse, and things like intimidation and bluffing.
• The role of strength vs dexterity, the difference between 'intelligence' and 'wisdom'.
• Most natural traits, including brain makeup personality and body type are determined by genetics but some small changes can be made over time.
• When it comes to performance of skills natural talent plays some part but the overwhelming majority of influence comes from which skills you learn.
• Sometimes things boil down to shere dumb luck. All you can do is make the best decisions you can under uncertainty, don't take it personally when something improbably bad happens but also minimize the expected consequences if you roll a zero.
• Most things boil down to the judgement of the guy in charge. (It's not what you know, it is who you know, and whether you are sleeping with the GM.)
• It is really hard to do stuff when it is dark.
• The best way to improve your social skills is to go around killing lots of people and apply what you learn from that to diplomacy, bluff and intimidate...