Right decision but struggling with outcome.

Background - long term sexless marriage with 2 almost teenage children. Rub along okay but very much flat mates. No sex for almost 10 years. Last year I hooked up through Tinder with a much younger guy (by almost 20 years) for sex. Mind blowing but after 3 times I could not handle the deceit and ended it. As well as feeling guilty I also worried that I could not handle casual sex and that it would end badly for me too especially with the age gap. Trouble is I have not been able to park that decision. I play the sex over and over in my mind and almost feel I made the wrong decision. Almost like I turned down an opportunity. Need some encouragement that it was the right thing to do and its simply a distraction from the bigger problem which is the state of our marriage.