>>12673908same here. I returned to school and started at the pre-algebra level (having forgotten basic mathematics in high school) ace'd every math class since. I'll be taking calculus 3 this semester then transferring to university for CS.
That said, everything Professor Doom said was basically true. Plenty of students don't go into these classes with the correct attitude. I did well because I was sick of being a NEET and knew that if I failed I'd may as well kill myself.