I think I’ll live another day

I am surrounded by some really sad people. I have a feeling of disbelonging. I'm like an outcast living near them. It's not like I'm really happy or anything... I just can't complain All the time, or cry myself to sleep every night, or even think about hurting myself. Questions start appearing when I see this behavior:
How is it that we define our existence only by how much we suffer?
Why is it that when we are asked to name a defining moment in our lives we almost always choose a hideous one?
Why is it that it is so much easier for us to cite the worst experience we have ever had than the best one? I dought there are just more of them.
I heard quite a few people say that a real person can't be a happy one. I can't agree. But I really don't know if I can honestly say I disagree. Because there is one person I know and that is myself.
I see this every day:
We always say something like: If this passes I'll be happy. Or: After that, I'm a free man. Well, this never seems to happen. There always comes the next thing. And the next thing... and so on. Point is we never seem to be able to just say: NOW I'm happy.
We always use the future tense. We live by future. Sometimes by past. Still one question remains:
Why do we always seem to say: I think I'll live another day.