"All the code you write is wrong."
Every time I read about a "best practice" or the opinions of highly regarded (to many) developers, I always am amazed at the different opinions in response. This isn't bad. In fact, I think it's pretty cool we all share differing opinions and what works for one person may not work for someone else. I find it refreshing to see all sorts of opinions that propose different ways of doing the same thing.
Thus, my mantra from now on is:
"All the code you write is wrong."
That works for me considering I never met a developer who always thought what they wrote was perfect.
I strive to write "good" code but I'm always ready to hear it is terrible and could be done a better way. That's why there are smarter people than me alive.