Happiness

They say that happiness is 50% determined by genetics and the rest is how you perceive your situation. I have always viewed the glass as half full and I've generally been a happy and carefree person. I have learnt to appreciate what I have, the situation that I'm in and the simple things in life. And when things don't go my way or how I'd like them to turn out, I try to think in other peoples shoes and think positively. But there are of course things that make me sad. Some things that I know are out of my control and some things which I have done that I wish I could take back. Regret is the worst thing to have in life and it's being so true for me :(....Yet it's also true that when happiness comes after a period of sadness it would be that much stronger, so maybe it's ok to be sad and sadness is perhaps an integral and necessary part of life. I wonder if there would be happiness if there is no sadness?