I spent some time reading The Science of Programming by Gries.

Sometimes when I'm in a particular mood for strictness, and I don't need the sheer power of Lisp nor am I doing anything that requires C++ (which occurs more and more often these days), I use Haskell for a different kind of thinking.

It feels great to be able to reason (as well as I can) about the correctness of my code. I haven't gotten much yet out of LEAN and other such things, so for now Haskell is my stopgap. It still has bugs, but when using haskell I try to be in a Bourbaki-like ultra-rigorous mindset. If it compiles, it is probably correct, and the idea is to stuff as much of the content of your program into the type system as you possibly can.