''We’ve all started a sentence with the phrase “Won’t it be great when…” (I go to college, fall in love, have kids, etc.). Similarly, we often hear older people start sentences with this phrase “Wasn’t it great when…”

Think about how seldom you hear anyone say, “Isn’t this great, right now?”

Surely, our past and future aren’t always better than the present. Yet we continue to think that this is the case.

These are the bricks that wall off harsh reality from the part of our mind that thinks about past and future happiness. Entire religions have been constructed from them. Whether we’re talking about our ancestral Garden of Eden (when things were great!) or the promise of unfathomable future happiness in Heaven, Valhalla, Jannah or Vaikuntha, eternal happiness is always the carrot dangling from the end of the divine stick.

There’s evidence for why our brains operate this way; most of us possess something called the optimistic bias, which is the tendency to think that our future will be better than our present''.

http://theconversation.com/why-you-shouldnt-want-to-always-be-happy-62086