Let's face it some men choose to be restrained in their sexuual acitivities by their own consciences and also by the restraints our society imposes. That is a choice. Others, choose not to be bound. They are unfaithful and have chosen to be so.
However, most of us, if we are honest, recognize that simply being married does not get rid of that animal lust we all carry with us. "In my mind" I am shamelessly promiscuous; "in my mind" I enjoy fucking sexually attractive persons of both sexes; and, I am happy to say, that no one gets hurt. In real life, I chose to "follow the rules"and be content with the delightful lubrication which my brain and body manage to deliver to my cockhead and which my generous foreskin contains long enough for me to get to someplace where I can insert a finger and move it through the slippery lubrication before I sop it up with a tissue. I often wonder if the person who triggered all that in me would be pleased to know that he/she had had that effect on me.
For many years I have had two friends who have had the hots for me,as I have had the hots for them, for many years. I am happy to know that I remain sexually attractive to them as I hope they are complimented in knowing that they are sexually attractive to me. Only in my mind, and I presume in their minds too, have we had sexual relations and I believe our relationship would not be broken if I was to cross the line with either of them. They know my family and I know theirs.
In summary I would say that knowing who and what you are sexually and acting on that are not the same. I need the friendship of men;, particularly of men such as my two friends; for many years that has been enough.
The brain is our most powerful organ of sex; wise persons recognize that and get some satisfaction on both sides of their sexuality that way. And, IMHO, the wise person will keep the secret thoughts to himself.