Why do We do what We do?

Why did I choose to write my book about Sylvia Plath, instead of Tom Sawyer or tiger sharks or vegetarians, or someone or something else? Think about it! Why do we choose to do what we do? The answer may not be as simple as one might think. "Well, because I can," someone might say. Of course, we have to have the ability to do something, but history shows us we can all do amazing things. Why choose one thing over another. Maybe it's because we're told to do it, ordered, commanded, like with a homework. But, we could rebel and say, no, can't we? Maybe it's just chance, just something that happens without any reason, just "pops in our head." Maybe we select to do something completely on our own, create it without any influence from someone or something, like we're a genius. It's in our genes or unique personality to do it. Or, maybe we research something we've come to like or feel curious or excited about and want to tell others. It just touches us. Or, from a spiritual perspective, maybe we're "called" to do something. Maybe it's our following our destiny or intended life direction, doing what only our unique self is to do, invited but not demanded or commanded to do this by some supernatural force, energy or Being, contributing to somewhat of our vocation, if we choose to follow it. Another possible explanation is that maybe we do something because it gives us a reward of some sorts. Maybe doing it will give us power, position or wealth. Or, maybe it's a combination of some of these or other explanations. I wonder what you think about why you do what you do. What do you think?