Should I pursue a career that interests me even if I don't have much aptitude for it?

I have a strong interest in the field of bioengineering for what it can potentially accomplish. However, in my own estimation, I have little aptitude for hard science and seriously doubt whether I can succeed academically in the areas necessary to enter the field. This self-assessment is based on my academic history, life accomplishments, and aptitude test results. My Should I try to pursue this career against the odds anyway, or should I accept that I don't have the intellectual capability to do so?