Why do we choose things not in our best interest?

Today's discussion about "why" do we do things to ourselves that we know are harmful really hit me. That is such a sensitive question that, really, no one knows the answer to. When you, Mr. Shapiro, gave the example of smoking for 20 years, you made me think of my family. ALL my family smokes. Only my parents quit 2 years ago. I remember I would ask my dad, who would smoke literally a pack a day, "why do you smoke?", and he would either respond "Because I like it", "Force of habit", "It gives me something to do when I'm nervous", or "Because it calms me down". He said that when he was 12 -- when he started -- he did it not even because he liked it, but it was because it was what everyone else was doing and by doing so he was going against his dad, so it was almost like a rebelling sort of action. That has to do with the conversation about being in control, showing that you can do what you want even if people tell you no. Then you brought up the example of "your parents tell you to do this and this, and at one point you're just like f*** it, I'm gonna paint". Now, in my case, this is music. Why do I do it, knowing that I can have much bigger possibilities getting a job doing God knows what and studying who knows what... and yet I choose music. Why? Because it's what I like. I don't see myself really doing anything else as well... or happy doing anything else. I think people sometimes make choices that aren't necessarily harmful to them -- like, music isn't harmful to me -- but it might not get me as far in life if I don't make it big, simply because it just makes me happy and motivates me. For that reason of finding something that makes them happy and drives them, people do something that they know might not be in their best interest.