Are you really, 100% honest with your spouse, as in "I think I might have watched too much porn" or "I just can't stand our child, I think he's ugly and spoilt, sometimes I wish we didn't have any", or "I really don't fancy you anymore, I'm thinking about having an affair"...?

I would assume most people are not that candid with their partners, but that's the sort of thing you can discuss with a therapist.