This seems completely backwards to me. IMO, the way to go is focus on allowing yourself to do things, not forcing things through. Active willpower and use of "m

This seems completely backwards to me. IMO, the way to go is focus on allowing yourself to do things, not forcing things through. Active willpower and use of "mental toughness" helps much less than you think it does. Trying as hard as you can at, say, riding a bike quickly isn't that much more effective, and burns up much more long-term resources. Like, how I'd reframe the advice is to pull the "replace trying with awareness" trick from The Inner Game of Tennis. Take stock of what it feels like to do the "last" pull-up that you can, and then feel what it's like to do another afterwards.