Forget Yesterday and Think of Tomorrow. 

What's a sure of stagnation in your life? When you dwell on the past at the expense of the future, you stop growing and start dying. Note Ecclesiastes 7:10 (NKJV)

      Do not say "Why were the former days better than these?" Foryou do not inquire wisely concerning this. 

I agree with Laura Palmer's advice "Don't waste today regretting yesterday instead of making a memory for tomorrow". David McNally reminded, "Your past cannot be changed, but you can change your tomorrow by your actions today. "Never let yesterday use up too much of today. It's true what Satchel Paige said: "Don't look back.  Something may be gaining on you."
"Living in past is a dull and lonely business;  looking back strain the neck muscles, causing you to bump into people not going your way " (Edna Ferber). The first rule for happiness is to avoid lengthythinking on the past.  Nothing is as far away as one hour ago. Charles Kettering added,

    You can't have a better tomorrow if you are thinking about yesterday all the time. 

Yourpastdoesn't equalyourFuture.