Clay:

"Self-change" occurs without free will.

All "change", whether we're talking about evolution, volcanoes, disease,
education, or "personal growth", is entirely inevitable, caused by
physical factors, including in some cases the physical state of the
brain. The desire and ability to change are caused. We do what we
must, we either change or we don't. If we try and fail it means we
couldn't.

Knowing this can be an important determinant, it steers us away from
the fruitless concepts of free will and contra-causal self-blame ("I could
have done better but I didn't") to look at the myriad of causes and
potential solutions to our problems.

As for the degree of difference it makes (Free will vs. NFW), I'd
compare it to the difference between pre-science and science, in other
words there's a big difference. When people believed volcanoes erupted
because the gods were angry, they had to throw virgins into them to
appease them. Now we don't, and the virgins are happy about this
difference!

Ken