I often like to question the choice I make and spend time to evaluate if I made the right one. I found that it can be stressful and I tend to keep coming back to the same subject.
One way I found to reduce or avoid ruminating, it's to commit to the choice I made. When I find myself starting again to rethink a decision, I will say to myself, STOP. Then I say, the choice has been made, I will live with it for the next 6 months or 1 year. Only after that amount of time, I will allow myself to evaluate that decision again.