No. Changing your identity is much more powerful and sort of operates in a background process whereas willpower is more of a conscious foreground one and very difficult to sustain long term.

Read the book. It goes into some detail.

I’ve worked with thousands of people personally over the years to help them with supposedly difficult to treat addictions for instance. Willpower is fine to start, but completely fails in the long term. Identity change is the only thing I’ve found that works long term.

This might be a stupid question, but what is "identity" in this context?

I ask because when this subject has come up I realize I don't seem to be able to think up theories about myself so easily

Run a few test theories and see what resonates. Are you the kind of person who goes to the gym every day? Are you the kind of person who works on their hobbies at night? Are you the kind of person who binges Netflix between dinner and bed? Are you the person who cooks dinner from scratch, or orders takeout at every chance? etc. I think of them a bit like stereotypes but applied to myself, and see if I think I fit.

It’s not supposed to be descriptive in this case, unless it’s a reflection or self-assessment. For goals, it’s supposed to be aspirational, like a vision you cultivate for yourself. You can meditate on that self-image, or identify other people with that trait and associate yourself with them, etc. The idea is that you will violate your sense of self by acting against how you expect yourself to be.

I'll look into it. I think I acquired frugality from reading a few books that made me frugal.

I'd like other traits too.

First time I’m reading about a character trait walking straight off the page into the reader’s life..

People who consider themselves "gym rats" go to the gym because it is what they do.

People who are mountain bikers don't ride to keep in shape, they look forward to getting on their bike.

Those are easy to see, but there are few people who clean their dishes for fun/leisure.

I clean my dishes because I like having a clean / neat household, "I am the kind of person who keeps my space in order". I find that helps!

I have met some of them. And I can say for certain I find using a dishwasher more fun than washing by hands. Even if it's family time etc. etc.

No but there are people who pride themselves on always keeping a clean kitchen etc

True, but I take loading a dishwasher as a puzzle to do it in the most compact/efficient way, which helps with adding enjoyment to the process.

For years, I was "a person who liked to ride my bike 300+ miles in a day". Then one day I realized that was a lie, or at least only a half-truth. Then I realized that most of why I did it was that I liked to keep in shape, and to eat a lot.

Somehow you've made a step in the exact opposite direction of what seems to be encouraged here. Does it still work out for you?

It's more like discipline. You don't do something because you decide to become a person who just doesn't do that thing. It becomes part of your identity, rather than a decision you have to continuously make.