I have been using GNU Emacs since the late 1980s. It has been my life's editor, so to speak. At 59 1/2, it seems unlikely that I will ever switch to another editor. It's served me well. I am grateful to the hackers that created it.
I only just understood Emacs about a year ago, despite being a nerd for at least 30 years. I like to think I don't have too many regrets in life - but I'm kicking myself for not realizing what Emacs was way back then - or at any of the times I've tried it out in the past (writing it off as "a text editor")! Never too late though, and on the plus side I've now got decades of hidden Emacs goodies still to discover!
Best resources you’ve used to discover things?