for me there is a deep sense of struggle. When I cannot locate the true enemy my struggle is misdirected and can be destructive too (both against self and others) but I think it is through prayer and our life of faith that we are guided to understand who and what the real enemy actually is.
I do not think that sexual desire or any human desire is the enemy per se and I think that if our struggle is directed against these that we are doomed to fail.
I rather think that the enemy is the strange gulf that opens up between God and man whenever we 'lose contact' - which happens so easily in a distracting distracted world. Sometimes I see it rather like a march through the wasteland. God is always a step ahead (like the cloud and the fire in the Torah guiding his people through the desert) and the temptation is always to sit and rest and not to move on when we are called because nothing stands still in the life of faith and we are always thinking that this must be it: a place to call home. But it never is because God has 'moved on' and is calling us to stay with Him. This sometimes gets deeply exhausting and frustrating too because the other great danger (the greatest) is doubt. [Sometimes I say 'enough!' and stay put even though I know I am being left behind and that my family of God is already on the move. When the distance between grows beyond a certain point a spiritual despair begins to set in and then it can be months or longer before God somehow calls me back and I have to start the process all over again . . . .]
so I think the first real enemy is doubt (both doubt in God Himself but also in myself - the refusal to believe that I can ever have a place in God or am good enough to find a place in God). I think these two types of doubt are related.
I think the less we worry about sex or food or everyday stuff and the more we focus on God the more life will 'make sense'. When I am worrying about how often I have masturbated I have already missed the point and my worry is already driving a wedge between myself and God.
so the second real enemy is worry about practical stuff. This can drive us way way off course before we even know where we are.