The voice in your head is usually strongest when you first start changing.
Not because change is fake.
Because your past gave that voice evidence.
Broken promises.
Dropped standards.
Old patterns repeated enough times that doubt started sounding reasonable.
That is why the answer is not to debate with it all day.
The answer is to outwork its case.
Do what you said.
Then do it again tomorrow.
Then keep going long enough that the old argument starts sounding outdated.
More here: https://jimlunsford.com/discipline-dispatch-let-actions-answer/