Forget the past and focus on the present. If you don’t like the present, focus on the future.
If a man in line behind you at the convenience store buys a lottery ticket and wins a million dollars, do you kick yourself for not buying that ticket when it was your turn in line? Life is chaos; pretending things like this are in your control is useless. Punishing yourself for not knowing what you didn’t know in the past is cruel.
Your misery comes from your own self-imprisonement. Happiness will not come from a time machine. Rather you should work on keeping your ego out of the driver’s seat.