Oh man, I've so been there. One of my biggest ones was when I was 6 weeks pregnant with my first baby (surprise!!) and fairly sick, but had done okay for our first two park days. But on the last park day (Friday, the only day the 50th fireworks were happening, which was my biggest must-do that trip) I was much sicker than the other two days, and absolutely couldn't handle it anymore. I had to call my friend to come pick us up at like 5:30 PM because I was so done. I'm still a little sad about that, and it was 12 years ago! I don't always have meltdowns at Disney (almost like clockwork at Sea World, usually at the Sea Lion show, when I get hot, haha) but I had one last year too when I got frustrated, and it was so hard to recover from that! You just want to ENJOY YOURSELF, dang it!