Jesus tells us in the Sermon on the Mount that we're not to hate or lust, that how we think of people, in the depths of our heart, is huge. I was struck by this last night - when we lust after someone, or dwell in bitterness and hate upon someone, we are living selfishly instead of redemptively.
That person you're lusting upon is a child of God and you're using them as an object of selfish desire, instead of praying for their life to be raised and redeemed. I don't know if this is making sense, but it made perfect sense to me last night and I was really moved by it. I had one of those 'moments' where God really spoke to the depths of my soul. He told me that these are His children, and if I truly am walking in His Spirit, I will see them the way He sees them - not as objects of personal desire, but as people who are hurting.
Here's what He told me: Any lust or hate simply adds to their hurt, even if they don't know it, because you are seeking your own gain upon that person instead of their redemption. You may think it's harmless to them because they're ignorant of it, but it's not.
The fact that you're preying upon them mentally instead of praying upon them spiritually hurts them, because it removes you as a possible agent of change in their lives. You have, in a sense, become a predator instead of a healer, whether it's hating them, not forgiving them, judging them, or lusting after them.
(And, of course, there is the spiritual harm it does to your own relationship with God.)
Psalm 73:22 "I was senseless and ignorant, I was a brute beast before you."
When we dwell in the caves of hate and lust, we are living like an animal, feeding off the flesh of other people. (The pound of "flesh" we demand in our hate or the allure of the "flesh" we desire in our lust.) Either way, we are not living redemptively. He showed me that very clearly last night and I was changed and I prayed for people I know.
It may have been a momentary change, but these moments of change add up in the long run.