Good advice, but keep in mind that willpower might be a limited resource (it is[1], it isn't[2]). You do not want to spend it all while training for grit.

In my personal experience, willpower is indeed limited. But that's n=1. As with everything in life, moderation is key.

[1] https://www.wired.com/2012/10/mf-willpower/

[2] https://digest.bps.org.uk/2015/06/24/new-research-challenges...