How do I catch myself sabotaging my success?

You have started to see the pattern, the way you undercut yourself right when things are going well. That is a real turning point, even though you cannot yet stop it in the moment. Seeing the pattern always comes before catching it. You are further along than you feel. Right now you notice it afterward, in the wreckage. That is normal and it is progress. The awareness is slowly moving earlier, from after, to during, to eventually before. You cannot force that jump, but you can feed it by studying your own pattern with curiosity instead of shame. What tends to come right before you sabotage? A feeling? A situation? A certain kind of success? Start keeping a quiet note of each time you catch it, even if only after the fact. Write down what was happening just before. Over time you will start to recognize the early signs, a tightening, a doubt, an urge to pull back, and the recognition will arrive sooner. You catch the pattern in the moment by first learning its shape. You are already learning it.