What am I doing wrong?

For over 2 months now we have been letting Anne cry herself to sleep. I know it sounds horrible, but those with children will understand that sometimes you just gotta do it. Before I had a baby, I pictured myself to be the type of mom that slept with her baby, carried her all around in a sling all the time, and never ever let her cry. After I had a baby I realized I couldn't be that mom and if I tried Anne actually suffered. When I tried to be that mom, I was irritated and annoyed at Anne. Upset she didn't sleep long enough, upset she couldn't sleep without me there, and upset that I never got a break away from her. When I switched over to sleep and naps in a crib, I was a much better mom. I got the break I needed and therefore had a lot more patience to deal with her in general. Well, I have no idea what we are doing wrong. Like I said, we let her cry it out for naps and sleep over two months ago. And Anne has just not caught on. I thought when you let a baby cry it out, it was supposed to be 2 or 3 days of crying and then like magic whenever they were put down for a nap they fell asleep immediately and slept great. Apparently Anne did not read that book. She cries for 98% of her naps and going to bed. I do the same thing everytimg. We have a routinue. I don't "give in" and go get her when she cries. I leave her alone to cry herself to sleep. I can count on one hand the number of times I had gone in and gotten her out w/o her falling asleep. So, in therory, there is no reason why she should still be crying. Today, she has been crying for over an hour. I have no idea why. Again, I did everything the same as always but for some reason Anne just doesn't get it. I think a lot about going back and just nursing her to sleep every time or doing the Ferber thing where I go in and check on her every few minutes. I'm just at a loss...this method is supposed to have a 100% sucess rate and yet my child, who is otherwise perfect, it does not work for. Well, thank God for small miricles; after one hour and 15 minutes of crying, there is quiet upstairs. I think she finally fell asleep. I'll tiptoe around the house until she wakes up...