VQuintessence
Bro your logic is terrible you said its less dangerous if he feels like a failure instead of failing let me give you an example why if I was depressed because If he didnt meet up with a goal and felt like he was a failure he can always push past that feeling however now your protagonist cant do that he'll instantly die, whereas if he said I'll die if I fail at becoming the strongest person by 20 or 25 or even 30 he has time to meet up to that goal especially with the powerboost via the vow thus the vow will eventually come to conclusion if he succeeds whereas if with this vow of "feeling" like a failure he can die just through a depressive episode.