I don't really consider it a "cure" but the way I manage my perfectionism (and holistic completionism) is to simply re-frame my goals to not meet perfect but to get as close to perfection as possible. As long as my actions get me closer to my goal, I am satisfied. It's a very brute-force and reduced version, but another way to say it is that if you want to go North, just never walk South and iterate in steps.
Also, I've basically eliminated failure from my personal language. Any task that doesn't achieve the desired result is simply a delay and I re-adjust immediately to find a new tactic that will put me back on track. If the time-effort to proceed isn't worth it, I dump the effort and change strategies. I long ago got rid of the idea that anything I create is special or worth saving. Outcomes are what matter. It's a very pragmatic approach and eliminates the perfection tendencies because it gets things done.