Patience

I am good at compartmentalizing, and my patience is a perfect example of that. Let me explain.....
I have the patience of Job when it comes to training horses. I ask much, but accept any shred of correctness with lavish praise. But ask me to wait in line at the grocery store, and I seriously consider not eating dinner that night.
Explaining the minute details of what it means to be "in front of the leg" to a student may put me 'way behind in every other thing I have to do that day, and I will happily adjust my schedule, but having to deal with "customer service" over the phone for an issue with my computer will make me want to scream, and throw the computer in the pond.
So am I a patient person, or an impatient one?
I once took some film (you know, that stuff that you had to have developed when you took pictures with a camera from the dark ages?) in for said developing to a place that said "ONE HOUR PHOTO" right on the side of the building, and when the clerk took the film, he asked when I wanted the pictures back......and was surprised when I looked at him like he had three heads and said, "what do you mean?". He asked again if I wanted to come back "later" or tomorrow. I said, "look here, it says on the building 'one hour photo'...I am coming back in one hour. Patience is NOT my virtue".
But that isn't exactly true, because I DO have infinite patience for some things....just not for ALL things.
And what should be the limit to one's patience? There comes a point when it stops being patience and it becomes being taken advantage of. I have been taken advantage of a lot, and on many different levels. I try not to be taken advantage of more than once in any given way, but there again--when does it cross into cynicism, or general suspicion? But I digress......
I wonder what other people's definition of patience is?