If you are unhappy because you aren't rich, you ignore the most basic principle of happiness: It comes from the inside, not from the outside.

One of them was the best drummer i ever saw/heard. He had a room full of vinyl metal records
--snip--
He had to tweak (or kill) his inner self to match the expectations of the world of the rich, to stay inside. He fell for the plain old "selling your soul" thing.

The other lesson came from a poor friend of mine.
--snip--
He just said: "i smile".

EDIT 3: One last thing: The original wording by my poor, happy friend was "If you're always happy, you can't stop smiling. If you don't stop smiling, you're always happy". He described it as "something like a feedback-looped duality" (freely translated)