Seems like a great method of winning the lottery. I’d find a recent drawing (no huge regrets to undo), memorize the numbers and date, go back, buy the ticket, set for life.

If that’s not in the spirit of the question, I guess I could change my college major. The one I got hasn’t been very useful. Though, if I did that, I probably wouldn’t meet many of the people in my life today. I wouldn’t choose to do this for that reason.

I could also refrain from telling a certain flame I loved her. That caused a rift.