This is the #1 problem of introverts; you can only have so much social interaction before you collapse, no mater how much you enjoy such interaction.
There is no way to skip this 'cooldown' period, but if you learn how much you can take and how long you need to recharge, you can plan around it. I myself have asked my GF to not come over or leave a few days early if i was planning on going to conventions, even if we were going together, to allow myself to recharge so i could enjoy the time for all it's worth.
Luckily, my GF understood this (although not initially); a day of seperate break is better than getting overloaded and a shutdown during a 'date' or event (which takes a lot longer to recover from)
It is bad timing for the collapse to happen during Animecon, but there's little you can do.
If there is time left, just spending a day by yourself playing games, binging netflix or whatever should recharge you enough to enjoy the rest of the con.