Shopping excursion...

We did a bit of clothes shopping today. As you can see, Amara's got it all figured out. We hit the kid's section first. Amara enthusiastically filled our cart with clothes of the wrong size, and once she spotted the dressing rooms things got exciting. She ran into a room, closed the door and stripped down. She also attempted to run through the store in her undies.
There's always a point during shopping where I abruptly stop having fun. Suddenly I'm unwilling to try on any more clothes, and I may even survey items I'm planning on buying to determine if its worth waiting in line, etc. I get totally burned out and just want to get out of there asap. Why do I do this? It does seem to happen more frequently now that I have two kids to manage at the same time.... but I can't blame them entirely. I've always done it. Is it just me?