Why do I feel like I am not good enough?
You feel like you are not good enough because some part of you learned, early and specifically, that being enough was conditional, and no amount of adult evidence has gone back and corrected the original file. This is not a character flaw. It is an old measurement still running in the background.
The measurement isn't yours
Somewhere back in childhood or adolescence, enoughness got attached to something specific: grades, being easy to manage, not needing too much, performing happiness for an anxious parent, being the reliable one after a divorce. That attachment worked. It got you love, or safety, or at least less conflict, so your brain filed it as the rule. Decades later you are still measuring yourself against a bar that was built for a ten-year-old's survival, not an adult's actual life. You can be genuinely accomplished and still fail that old test every single day, because the test was never about your actual output. Notice the specific voice or scene that shows up when the feeling hits. It is rarely abstract, it usually sounds like someone.
Why this is not a flaw
This response made sense. Children who tie their worth to performance or good behavior are children who adapted correctly to an environment where love or attention was inconsistent or conditional. The vigilance you now call self-criticism used to be a working strategy for staying safe or staying loved. It is not weakness, it is a system that got installed under real pressure and never got the update notice that the pressure ended. The fact that it still fires under stress, in front of authority, or after any small failure means it is doing exactly what it was built to do. The problem is not that it activated. The problem is that it never learned when to stop.
What actually moves it
Insight alone will not touch this, because the feeling is not a belief you argue with, it is a prediction your body makes fast, before you think. What moves it is repeated, specific counter-evidence that your nervous system actually registers: a moment where you fell short and the people who mattered did not withdraw. Directly comparing your inner monologue after a mistake to how you would actually talk to a friend after the same mistake is more useful than trying to feel better in the abstract. If the double standard is obvious once you say it out loud, that is the tell that this was never really about your competence. Track situations where the feeling spikes for two weeks. The pattern in the trigger tells you more than the feeling itself ever will.
When this runs your life, it usually traces to one underlying pattern. For this, it is most often the Keeper rhythm, the thing under the behavior.