It’s better to hit a wall earlier, when teachers actually care how well you’re doing and the stakes are lower. Then, you can get guidance on how to start climbing that wall.
If you're learning for mastery, that implies that whoever's teaching or tutoring you will care how well you're doing. No matter what your level is, i.e. even if you need to be "held back" from acceleration because you've yet to achieve mastery of your current curriculum.
