Love.
I don’t know if that counts as “simple”. But despite all the work and emotional energy that goes into a loving relationship – be it family, friend or lover – love is essentially a simple pleasure. Even when you’re having the most difficult day, a fleeting image of that person’s smile or a memory you shared will instantly restore your energy and put a smile on your face.
For example, I get flashbacks to my childhood and the days I spent with my parents and that makes me happy. Or I’ll think of some crazy adventures that I’ve been on with close friends. Or various other memories with people I cared about that makes me laugh to myself.
As four wise men once sang, all you need is love.