The question in my view is a deep one. for me, it's a matter of what we think and feel, on the one hand; And what we do about it on the other.
Our actions & behavior will be judge by others, but we can judge our own thoughts and feelings before we do anything about them.

In keeping a Diary, I have found myself fearful of anyone reading it.- But then, God knows what I am doing. And the warfare is with Him and myself as to what it means to be holy?

Sexual desires and thoughts keep coming into my mind, leading to fantasy
and how I would like to have them come true. Then the price, & the results
of them, and the Law of both God and man over-takes me;- And I'm back
where I started.

Real sex vs fantasy is only a part of this war that I hope to win. So each of us must be as much help as we can in the fight, win or loose.

I hope this helps; Write a Diary.