DD had had a great day on Saturday last weekend, and we'd been out to an hour of a 2 hour nature event on Sunday morning (looking at pond life). But we had to leave that early as she was invited to a birthday party, which was larger than we understood (cinema and McD's for a few girls was actually a joint party for whole class of 2 girls, including our neighbour who is a very good friend of DD's but 1 class behind due to time of year timings and different school). So lots of noise. It also meant she did not bring DH to airport bus as normal (2 weeks away for work, after 2 weeks home). And we only got last 40 mins or so of school fair (they were a bit later home than expected).
She was getting upset at having used all her tokens too fast, not seeing toy stall (wouldn't when it was still open, then cried when it had closed), not getting her chance to get soaked in the "throw a sponge" challenge (after soaking a classmate) and about other children "skipping q's" (some were, some she was so over-wrought she couldn't see that 1 child had left a sponge-throwers gran in for 1 go and then was going back herself to finish her chance of a soaking).
I ended up carrying her out, in my arms, in floods of tears, as she just had had too much. Luckily, I had a suspicion this might happen (but no way would she skip the birthday once asked, nor drop previous plans). So we'd driven to school rather than walked, so I could take her to a quiet coffee shop to have a proper sambo and drink in the cool and quiet and darkness there, and then let her run off some steam in the playground en route home. Which meant we actually had a relatively peaceful evening and bedtime in the end.
It's hard to see, but all you can do is acknowledge their inability to cope with certain things (like a child screaming in the bookshop yesterday - piercing enough to give me a headache, but poor DD physically recoils when it happens). And have a back-up plan in your head for when it goes wrong (like allowing your DD go under the blanket, so she can deal with things herself and come back to herself when she is ready).