Hello!Right now I am going through a similar situation as you and as you mentioned in your post it only applies to some aspects of my life and makes it very hard to keep up with this way of thinking.Yesterday I finished listening to an audiobook called "How to be an Imperfectionist" by Stephen Guise which suggests a number of practices you can do daily,according to what fuels your perfectionism,in order to overcome this problem.I think it is worth checking out!Here is the link:https://www.amazon.com/How-Be-Imperfectionist-Self-Acceptance-Perfectionism-ebook/dp/B00UMG535Y?ref_=d6k_applink_bb_dls_failed I hope I helped you in some way.
Mindfulness is great and I use it all the time. I had some CBT as well. There are many self-help books out there that use tested techniques like that. I use The Feeling Good Handbook (by David Burns IIRC). The therapy did help but I think someone determined enough could do it on their own with books and websites.
That time was hell but with all the self-improvement I'm feeling pretty good at the moment. :)