Genghis Khan famously described the best thing in life was "to crush the enemy, to see him driven before you, and to hear the lamentations of his women." After reading Steven Den Beste's article on what is it to be American, I believe this is the "best thing:" to know yourself and to make the world accept you on those terms.
The first half of this is about honest introspection. Knowing yourself is a difficult undertaking, and it is often much easier to let others define what you should be. But I don't believe anyone can be truly happy if he does not know what motivates him or if he find that and forgets it.
The second half is about action, taking concrete steps to live in ones own way. This is in direct contradiction to waiting for someone to give approval, or to self-constraining actions in order to spare giving offense. And this second half is necessary, for to know is not enough. It is better to be. And one cannot be if defined by another.
UPDATE: Max suggests another formulation: to know and be yourself, with respect but not deference to the rest of the world. In both phrasings, there is an acknowledgement that the world and you will disagree, occasionally or often depending on the divergence between your views and the mainstream. I wanted to highlight the satisfaction that comes from being acknowledged and accepted, and thus emphasized the process of making that happen.
Max adds the need to respect the opinions of the rest of the world. I would say "with consideration but not deference" instead. Every part of the world is worthy of consideration, but large bits of it are not worthy of respect, IMHO. But in general I accept his formulation as an improvement, especially from a civic point of view.