While brushing my teeth

I just got one of those what am I doing with my life sort of feelings.

How am I making the world better by what I do?

How WILL I make the world better by what I WANT to do?

Am I selfish for wanting a career that I enjoy and that may not positively or greatly impact the world?

I go over these questions all the time.

The only problem is this time I am having a hard time coming up with answers.