If you want to be successful in life, you have to let go of the past and turn your attention to what is happening now in your life.
Whatever the past was, it's gone, there is nothing you can do to change anything that has gone before.
Although it's always hard to resist the allure of dwelling in what has become by gone, but if you want to move forward in life you have to forget your past.
In case your past was a wonderful one or better than now, then you don't have to continue wallowing in past wonders but appreciate the memories and move on with the present. Think of ways you can make the present more superb.
Moreover, if your past wasn't wonderful then let go of the past, learn from it and make this present overshadow the past. Just fold your palm and open again, you've just let go of everything, that's the trick.
Your past is like a far away house to your present now, you can only go there to visit and not dwell there but your new house is your present now. Don't waste your precious time on your old house if you don't want to regret later.
You're right past give us nothing more than regrets we should learn from our past and should let it go