If having the perfect design is preventing you from launching a website or completing a contract (and getting paid), you may want to re-think what you're selling/shipping/delivering.
Dans ses écrits, un sàge Italien, dit que le mieux est l'ennemi du
Great is the enemy of good. Perfection takes much longer than adequate. Most of the time, and by definition, Adequate is good enough.
If it is for work, someone else really should have the final decision. You do your job right, and get it as close as possible - but then you say "I'd like to spend more time on this, but I've reached a point where the changes will be minimal and the time spent will be great. Do you want me to continue?"
For a personal project, trashing work you dislike is fine, but I wouldn't do that to a client (or to my boss). It becomes very expensive and time consuming, and they're often looking for good enough.