Gee mate, my HS was all over the place, and I never got better than B's and C's (not that I particularly cared). I forged ahead in what interested me: math and its applications to electronics, then computing, and finally physics (especially quantum physics and, to a lesser extent, relativity).
Find the beat of your inner drum; let that drive you, and the rest will take care of itself. I waited a couple of years to mature before going to university, did a degree in applied math (including computing) while working in a nowhere entry-level job (but they paid my university fees and gave me time off). With my inner drum and studies aligned, I was a straight honours student and was headhunted for a job before graduation.
Now I am 71, and in an assisted living facility; you know what I remember of my possibly misspent youth? Going on long walks with my then best friend around Mt Cootha in Brisbane, Australia, and Mt Tamborine in the so-called Scenic Rim near Brisbane. I wonder what those who got all A's in HS remember?
Now is the time to enjoy your youth and discover your passions. The future will take care of itself. B's and C's are good enough to get into a decent university.
Thanks
Bill