I would dip my toes into FP occasionally (but very, very briefly) for years. I bought a book on Scheme in 1995, to give you a sense of how long I wandered in the wilderness.

It wasn't until I discovered Erlang in 2012 (thanks, Seven Languages in Seven Weeks) that I finally found the motivation, aided in no small part by the fact that it's a very simple language and it's designed for server programming, where I've always been happiest.

I still haven't graduated into category theory or type theory. I still don't know the difference between a monad and a monoid. But functional programming really speaks to me, because I have an old, tired brain and I need pure functions wherever I can employ them to keep things straight.