To be honest, I never really thought about it, because everyday for me is like a blessing. I'm always thankful for being able to wake up every day, knowing I was given another day to live. I'm always happy with everyone around me (well... sort of), and I never really hold grudges for a long LONG time (except for that one person...).
I know this isn't really much, but THE happiest day of my life was giving my mom a surprise birthday party. It wasn't really my idea, but her co-workers brought it up and my dad and my brother went along with it.
Basically, my parents were supposedly fighting with each other, and they never really resolved their issue. I called her and told her my brother had a tummy-ache and dad wasn't around; he "went to party with the choir from church," and her response? "Why is that old hag always hanging out with idiotic people?!" I thought it was funny, and it was a ruckus when we all were getting ready to surprise her when she was in our driveway.
I remember clearly how everyone popped out and sang Happy Birthday to her when she stepped in the house with an angry face; it changed and her expression was speechless. Her hands were on her hips after we were done singing, and she asked, "Why are you guys being like this?"
That whole night was amazing, because everyone was drunk and sang songs. Everyone was happy and smiling, and it was something that I've enjoyed watching.