The only thing that motivated me during the MCAT was realizing that for every hour that I wasn't studying, some other kid was already in the library learning things I didn't know yet.
That motivated me to push harder, because I knew that while I was slacking, someone else was getting ahead. Aaanddd I wasn't going to let that happen.
I know it's not a competition, but sometimes you need that extra push.
Also, I took the MCAT twice and scored 5 points higher (and only spent 2 months studying for it the second time around). The best tool that I had was a study buddy. They were studying for their DAT, but the accountability of showing up to the library everyday and pushing each other REALLLLLY helped.