How do you get over self-doubt (when it comes to academics)

I am more of a right-brained kinda gal. :)

I managed to get through biology in university just fine (pulled off an A-), but chemistry in high school was another story. I got through it, but never wanted to go through that experience ever again.

Fast forward many years later: I have a degree in pysch and one in education. I was thinking about venturing into the sciences. Medical Radiation Tech, to be more specific. I would really like to upgrade my Chem mark before applying, but I am afraid that I won’t be able to hack it.

Story of my life, I give up before even trying…