Getting motavated for learning help! (Freshman in highschool!)?

Hi. I'm a freshman in high school (a girl, if that makes a difference...), and my first semester did not go so well. I get mostly B's, one A, and a C. Now, I know, and have been told numerous times by my parents and school consoler that those grades are not good enough to get into what my family and I would consider a good college. The truth is, I really have no been trying. When I try really hard is when I get A's. Lately, I haven't even changed for gym which is leaving me with a C. A C in gym! So what I'm asking is not what's the secret to good grades, but rather, what's the secret to motivation. How do YOU motivate yourselves to study, and take the time to do quality work? I could really care less about mitosis, and how to conjugate parler in french, so how do I make it interesting for myself?