If you are perfectionistic, you soon feel disappointed at your poor performance and anxious about improving it. Suppose that instead you tell yourself 15 laps is good enough for now. You accept the possibility that you may never be able to swim 20 laps easily, if at all. So you continue swimming without anxiety. You don't necessarily stop trying to improve, but you swim for fun and exercise and relaxation-for however many laps you can.
Perfectionists often miss out on fun, relaxation and satisfaction.
Set strict time limits on each of your projects. This technique reduces the procrastination that typically results from perfectionism. Suppose you must find references for a term paper and also study for an exam. Set time limits. If you stick to your time limits, you won't spend the entire day searching for elusive references, nor try to study late at night when you are too tired to be effective.