Honokooooo! *hugs* I missed you! Welcome back!

And I second everything Honoko said (coming from the girl who got a degree in engineering physics and is now getting her masters in linguistics). Junior, I wouldn't worry about setting your goals too high. If anything, worry about setting your goals too low and not accomplishing what you want to in your life. I think that wanting a career that will help people is fantastic, and whichever area you choose to study, there will always be opportunities for you to volunteer. I would say, find something to study that you really want to study. If you don't know what you want to study, try a bunch of different things out, and talk to people who work in those fields. There's no shortage of ways for you to help other people, and in the end, the most valuable thing you can give to others is your time.