Well, success and failure might need to be defined.
But I'll go by the balance of grades vs actual learning.
See, back in high school, I got shitty grades in some classes, but learned a lot anyway. Art was one of those. Was never willing to stay on task, I would get a wild hair up my ass and do what inspiration drove me to. So, bad grades. But the teacher was actually good at teaching techniques, so I learned a lot anyway. I call that a success.
Spanish though? My grades were meh to decent, Bs and Cs. But only by virtue of being good at translating on paper with a dictionary in hand. Never did reach a point of being able to carry on a conversation in spanish. I call that a failure.
Maths in jr high and high school were barely passing. Didn't learn shit, and didn't retain what I did learn. Utter fail. But then, in college, I had to take some of the math again, had a professor that matched my needs very well, and got both good grades and learned a lot. One of the most satisfying successes in my education ever.
But I was always absurdly good at language arts in primary education. I could crank out As and Bs with almost zero effort. So I succeeded by both standards. It wasn't as satisfying though.