Is there any evidence that the author's life experiences aren't valid until someone documents them in a laboratory setting?

Yeah, sort of. In terms of saying "this works for me so it works for everyone" anyway

https://en.wikipedia.org/wiki/Anecdotal_evidence

It's less of a warm up and more of a habit. You've done it once, you'll be more likely to continue to do it throughout the day.

Current understanding of willpower is that does, indeed, function like a "muscle".

I got this from reading a few books and articles and it might be wrong, but it's my impression.

Training willpower in general is one thing - doing "warmup" just like a real muscle it's a different thing.

Actually, there used to be research showing that ("ego depletion" it was called) but it is getting more and more controversial because it's been quote a few years now and nobody managed to reproduce the effect.