Today I didn't yell

Today, after half of our grocery trip was spent with Graham crying (the other half of the time he was eating a donut, which may or may not have been a good idea) and the crying only got worse when we got in the car (which we walked to sans jackets in 25 degree weather), I made a commitment not to yell.  One of the coping mechanisms I've read about is counting to 10.  I counted out loud (albeit, quietly) to 344, which was the amount of time it took for us to get home.  I felt tired and angry and sad, but I didn't yell.  The crying continued for another 30 minutes in the house because he wanted up.  No he wanted down.  He wanted water.  He didn't want water.  He wanted in his room at the same time he wanted out of his room.  I felt flustered and nauseous, but I didn't yell.  We made the decision to "lock" his bedroom door, which made him FURIOUS.  He cried and screamed for 40 minutes.  But I didn't yell.  And then it was quiet.  I panicked, thinking he passed out or knocked himself out, so I opened his door.  He had tired himself out, climbed in bed, and fallen to sleep.  It's 2 hours before nap time.  We're going to be totally screwed this evening if he sleeps for any less than 2 hours.  I feel nervous and stressed, I'm not going to yell.