Our past serves as a mirror where we can look at the events which got unfolded owning to our decisions and actions (good/bad) which led us to the present situation. If you are having a good life as per your wishes then no need to worry. However if you are not happy with your life, then you got to find out the reasons for your unhappiness or dissatisfaction. Rather than blaming others, you have to figure out what have been the shortcomings within you. For that, the best way is to reflect upon the past, identify your mistakes and then learn from them.
There is a causality theory which says that for every effect there is a cause. If the present situation is unfavorable then surely there is a definite cause for that. Obviously it would have to do with your past mistake in terms of your actions or even your wrong thinking process. If the unfavorable situation is still continuing with your life, then you can conclude that your philosophy of life that you have been implementing is not correct.
Next, you need to introspect and decide upon what you should have done to get the things right. Of course, if you would have done right things at the right time in the past, i.e if you would have avoided your past mistakes then surely things should have been right and favorable today.
I remember watching the movies like The Groundhog day, Time again, The Butterfly effect or the Time Machine, where you can go into the past or live the same day again, avoid making such mistakes and reorder things in your life
But ground reality is not like those movies. In truth the arrow of time only moves forward, so it leaves us with no option to go back and correct our moves in the game of life. But reflecting on your past can give you a fair idea of how you have been playing this game.
It is rightly said that mistakes continue to remain as mistakes until you learn from them and make corrections in your attitude and actions. Once you learn from your past mistakes and start implementing those learnings then as per the Causality theory, you will soon be able to overcome the effects of your mistakes and live a better life!