I see what your saying sunnydays but I think there is still a huge difference. One being that generally a badly behaved child is to be expected during their early childhood development and most posts on this forum are about parents not working hand in hand to correct this behaviour so the problem is the adult and can rub us up the wrong way much worse than a naughty kid which we expect a lot more in our job. Makes it harder to shake when a parent is part of the problem. Also, when working outside the house, you may have an ass of a boss or irritating co-worker but when your work day is over you come home to somewhere completely seperate. Working in this job can be very isolating and at the end of a bad day there is no seperate space and it can be harder to switch off the last 9 or 10 hours as it was in the same setting.
I think you need to make part of your routine self care. Nobody is going to look after you so you need to make yourself a priority. Also try changing up your daycare day a little bit with a different routine and different activities. Have a music time with YOUR favourite songs and dance around, have a big sensory activity like shredded paper and let them go crazy and then after just vacuum it up. You can play as a group, they will need less from you and they will be super excited and happy which will rub off on you. It will also tire them out for naptime and hopefully then quiet time will be quiet.
Keep your chin up. I get it that friends don't understand, so be sure to come and vent here. We will always give our spin on things and try to help you on these down days...