Somebody of psychologists once said "A really happy person is the person who can live now and here...
Just think about it... But we, on the contrary, remember either our past or imagine our future...
Someone was happy long ago and tries to keep this blessed state in the depth of his soul, not wishing to move ahead. Others cannot help thinking about former unfortunates and mistatkes, or may be about some grief. These thought eat away our piece of mind and again we are stuck in the past...
On the other hand, some people live by the future. They think: Well, tomorrow I wil get up and start a new life! I will become wiser, honester, fairer. Since the next month I will begin running in the morning, visiting gymnasium, pool. etc. We are waiting for a new Monday, month, New Year to start a new life! So we are living just by our hopes, thougts, intentions and that's all. The most terrible is that this "tomorrow" can happen never...

So, the only right way is to live by the present!