I hope no one minds if I throw a little spanner in the works - I agree with everything here I have seen so far, there's just something I think is worth adding. I think that whatever it is you define lust as, and whilst dwelling on thoughts and circumstances that feed temptation to do what would be unholy for the present time is definitely out-of-bounds, one has to - somewhere in the background - also realise that desire - on hold - is ok.
It's a rude shock when you reach marriage and everything you've trained yourself to see as bad and sinful and no stay away from that, is all of a sudden not only ok but in fact what you're supposed to do. Everything has to be redefined and the results can be really messed up if you had a wrong view of sex in the first place.
Sex is not bad, evil, or even sinful to desire. It is a normal bodily drive given by God as a gift. It's a good thing. Sex..and other activities... outside of marriage is the unintended abuse of this gift, but this shouldn't be confused with sex being bad.
I'm reminded of something I've heard some friends of mine say to their four year old, which makes a good example. Occasionally, the kid observes his parents drinking coffee, and asks for some. They don't tell him "no, coffee is bad - yucky, you don't want coffee".. what they say, and I've often heard him repeat in his adorable little voice, is "coffee is for big hands".. and they compare hands.. "you've got little hands, see? Mummy and Daddy have big hands". When he sees coffee now he faithfully repeats "Big hands - I've got little hands, see?"
My point is that whilst avoiding tempation and emphasizing the reasons to do so are important, it's also necessary to make the distinction that the sentiment ought not be "No, that's bad. Don't want it." But rather "Not yet. I want it, so I won't spoil it".
I say this stuff not as one who has it together but as a complete hypocrit. But a hypocrit who knows the truth none the less.
Good luck. xx