I think its common to find escape when things aren't working well in a relationship due it to an A, or just the normal crap in any of them. WE can always escape to our minds, sometimes fantasizing about another person where the current problems aren't there.
Thinking about it and doing it totally different things. When RAH relapsed I did think about it - really just to escape the that situation. I did not, because I am aware affairs and cheating never end a good place. I simply didn't need to add more destruction to my life.
Much better to resolve the problem with in the existing relationship or move on if you can't.