1/ Even though I know better, I'll often write my own solutions for problems I grok even though existing solutions give me 90% of what I want and enjoy Linus's Law. Yet, for things I'm not yet used to (e.g., react) it's time to import the most popular lib on @github.
2/ Granted, the things I grok are generally #datascience-related, and those problems don't enjoy obvious errors. But still, familiarity breeds more than contempt -- it breeds useless perfectionism sometimes, too.