Outgrowing a mentor isn’t betrayal. The good ones were hoping you would.

Somebody who taught you well was aiming at exactly this: a version of you that no longer needs the lessons. Moving past what they can give you is the result they wanted, not a verdict on them. The guilt that shows up is usually about the relationship changing, which is a different thing from it ending.

You can move on and stay in touch, because those are not opposites. Tell them what you are doing next and what of theirs you took with you. Then ask who they think you should learn from now.