I struggled a lot in math too. Got a D in calculus, nearly dropped out of high school. I'd absorbed my dad's excuse, "I'm bad at math." What a crock of shit. Turns out, I was bad at doing work in absence of motivation. But my parents didn't believe in ADHD, so I couldn't have that.

Went back to community college after some time as a web dev, and had a teacher with a booming voice and a gentle attitude, who explained that we were going to be doing a lot of homework. Like your instructor, he'd spend class time working problems, and then I'd go home and do an hour or two of homework every night while it was still fresh. That kicked off a trajectory that resulted in a PhD and a very fulfilling job as a mathematician.