Because I've been interested in astrophysics since I was a kid. Psychology is only a relatively recent interest. I'm almost always watching some kind of documentary on space phenomena, never have I sat down and watched a Psychology program (Criminal Minds doesn't count, not that I watch that show).
I watch CSI. Is that count as psycho?
But either way its kael's call. I like space too. If you want to be a rocket scientist, then go for it.
Its your life. No one should decide it for you.
You can ask for advice, but you must make the decision.