Getting to 90 days clean is a great feeling, and I want to share what helped me.
I had started the 90 day chart in November 2009, but I kept falling. I couldn't put my finger on it, but I would go for a few weeks - and then fall, a few weeks - then a fall.
Then I realized what I had to do, I had to not make it an "all or nothing". I told myself, "you can fall 3 times over the next 3 months. You can do them whenever you want, but only three times."
Needless to say, that's really what did it for me - giving me that little bit of breathing space created a world of difference for me. I fell once in the first month, but because I didn't have to go back to day one, that gave me the boost to keep on going.
Before I started this, I would fall once and I would think, "what the heck, I fell today, I might as well do it a few more times before I have to start over again tomorrow." Then I'd do it 3-4 more times THAT DAY!
This way, I had an incentive to stop myself after that first time, and that gave me the strength to complete a full 90 days clean. Whenever I had a pull, I'd say to myself "you only have 2 more times to fall, why not save it for some other time." And that was enough.
The one thing I can say to all those people still struggling, is that it gets so much easier after you hit day 30. I guess your brain's been wired enough that you've built up enough willpower to stop yourself.
The other thing I can say is that it is absolutely essential to have a strong learning seder - particularly of things you enjoy learning. I learn Daf Yomi, and that gives me an extra boost to just keep it all out of my mind and make me stronger.
I also can't stress how much better my relationship with my wife has become, now that I see her as the only woman in the world really.
May we all have the strength to keep our desires where they belong; channeled towards our Avodas Hashem!!