Agree with the enforced nap! That's the only thing that works when my 4 month WCS turns into a Tasmanian devil around the house.
I can normally tell when she's over-stimulated and about it lose it as the whites of her eyes get a pink/red tinge to them and/or she starts panting a lot. I wonder if anyone else sees this with their cockers? That's when I end the walk, play, or training and pop her in her pen for a nap. She might bark or whine for a minute or two, but as long as we ignore her and give her some space then she falls asleep and wakes up in a much better mood!
This works most of the time, sometimes we have to put a frozen carrot or kong (filled with liver paste or peanut butter) in with her and the licking normally brings her down enough to sleep. There is of course the odd day where nothing works and I just pour myself a glass of wine and seek higher ground