self-expression
During a conversation today I had a bit of difficulty describing what it means to express oneself. After several false starts that kept falling back on circular definitions, eventually we arrived at something that seemed to fit: doing something that makes one feel alive.
On the face of it, it seems rather silly to think of any activity as something that makes one feel alive; death is the literal cessation of activity, so by extension, any activity should serve to remind one that one is, in fact, alive - or at least not dead.
But being cognizant of the fact that one is alive is very much not the same thing as the feeling of being alive. I think anyone would agree that filing one's taxes, say, does not uplift the soul as does attending a great violin concerto.
It's probably safe to say that self-expression is a fundamental human need, right up there with survival. No human culture can flourish without striking some balance between these mutually incompatible drives. A nation entirely composed of artists and philosophers would eventually die of hunger or conquest; a nation of warrior-engineers with not a poet among them would eventually lose the will to build or fight. A balance must be struck in order for civilization to develop and be maintained.