Whenever I start caring too much about something, I pull up the "pale blue dot" image (https://funnyjunk.com/The+pale+blue+dot/funny-pictures/52789...) and remember that I will die long before Voyager will make it even 10% to the next star. All of humanity, including us, is just a tiny speck in an unimaginably vast and uncaring universe. Some people find that terribly upsetting, but to me it also means freedom because nothing matters very much anyway.
So when you feel perfectionism exerting its insidious pull on you, zoom out and remember that "it is not that important".
On the same theme, when I was a teenager my dad told me, in passing, to try to not to be the person caring the most about something. It has stayed with me since.
I'm not to keen on motivating myself through nihilism, because I don't think humans are really supposed to work like that. When I start caring too much about something, I try and reevaluate my goals instead. e.g. what I think the good things in life are to me, and whether what I'm doing is genuinely going to get me there.
So when you feel perfectionism exerting its insidious pull on you, zoom out and remember that "it is not that important".