Last time I was really happy for real was probably in HS (so over 10 years ago). I had a gf, was popular, successful at school, in many clubs, loved the school I went to, and all that.
Looking back, that's when the bipolar mood episodes started to become apparent though. Starting sophomore or junior year, I started missing many days just feeling like I couldn't get out of bed. Grades started to slip some (relative to where they were before) and I started SH.
But I'd still say that was probably the last time I was really happy because I felt like was in charge of my world. Life got too shitty and complex after HS and I'm just not equipped to handle that.