When I was applying to colleges, I already knew what I wanted to do with my life. I think that's what you need to do now, not so much as to what you're good in, subjects can always be learned, you really need to sit down and find out what you see yourself doing 5-6 years from now. I knew since I was little that I wanted to be a surgeon, my parents made it clear to me from a very young age exactly how tough it would be. I graduated undergrad from Stanford c/o '92 majoring in Chemistry, minoring in Biochemistry, and went on to Stanford Med, and graduated as a trauma surgeon. So my advice to you, coming from somebody who has attended both undergrad, and grad school, really look at how you see yourself in the future, and what you see yourself doing. Don't look at what subjects you're good at, and what you're not, as I said, subjects can always be learned. Further, a lot of the pre-req's needed for grad schools aren't used, at least in the medical field. For instance, Organic Chemistry was a pre-req in order to apply to med school, and take the MCAT, however, I didn't use any of it once I got in. So basically I'm saying, don't rule out different opportunities based on what subjects you're good at.
