“I've promised myself I'd change so many times I don't believe me anymore.”

The promises to yourself have piled up unkept until your own word has lost its weight with you. That's the real damage — not the unbroken habit, but a self that no longer trusts itself. You rebuild it the way you'd rebuild trust with anyone you'd let down: not with a bigger vow, but with one small promise, kept, today. Credibility with yourself is earned in evidence, not intention.