Johnny Bench wrote:
I know people who have done it, felt guilt-free, and maintained a good marriage.
My rambling advice, as someone who's been through all of this:
Make sure the person you fool around with doesn't think you're going to leave your spouse for them. Come to grips with the fact that no one person is able to fulfill all your needs. In that vein, do an honest assessment of how you'd/you'll feel if your spouse fools around.
What if you suspect your spouse fooled around once in the past and you are presented with an opportunity to "get even". I know screwing another person makes you just as bad and probably wouldn't make things better but it seems to be an answer.