I reckon you're misunderstanding stoicism if you think of it as mental gymnastics. You're implying it is a practice of self-deceit or indulging in irrationality.

Stoicism is largely about accepting things as they are and letting go of the illusion of control. This, if truly integrated in your outlook, is the opposite of mental gymnastics. Said otherwise, you'd have self-awareness to understand your predicament and cut through it. Believe or not, you and Marcus Aurelius share the fundamental human condition, despite him being what you'd consider a "top performer".

Would you consider Cognitive Behavioral Therapy a practice of mental gymnastics? After all, Aaron Beck was inspired in part by the stoics.

I wish you find peace, don't be too hard on yourself.