The Potty VS The Mommy

I think that Potty Training is the arch nemesis of mothers everywhere. Correct me if I am wrong. I can deal with just about everything else, but this Potty Training thing is KILLING ME!!!! There are a number of issues at hand:

1. How was I supposed to know HC was/is ready? He turned three a couple weeks ago, but we have been battling this for a year and a half! I started him when I was told I was "supposed to start potty training." I am afraid we started too soon, and now we have messed him up. For life?
   
2. The preschool says he cannot attend if he is not fully potty-trained. WHAT?!? Talk about pressure!!!  For me and for the little guy!!
   
3. I feel like we are going in circles, success one week then two steps back the next. I hear stories from friends whose kids potty trained in weeks, even days!!! But I tell you... we've been at it for a year and a half!!!

And so how exactly does a mom figure this out with her first child? How did you? I'd love any insight you can share!!!