Grassissinging, you put it all so well. and I wish you the utmost enjoyment in your cuppas next week.
I agree with everyone who has said "it's not a competition" "the problem is this relentless comparison" etc.
BUT, except in exceptional cases, the life of a WOH non-parent-non-carer, AND the life of a SAHM of a T child, do include downtime that in the life of a WOHM just get swallowed up. Yes, my child minder is physically with my children when I am not (and she is ace and works bloody hard, far harder than my P did when he was SAHD). But she doesn't do school admin, doesn't agonise about that weird rash on the back of the neck, doesn't do night terrors, doesn't mend or buy clothes or do packed lunches, etc etc etc. If I didn't have children I would consider myself knackered when I get back from work after a 12 or 13 hour day. As I do, the next shift is just starting. No breaks at work, either, or I will stay there longer which I can't afford.
I took a week off to potty train dd2. It isn't the job of the CM or the preschool to run around with a potty for the days it took to get it sort of bedded in (fingers crossed). I potty trained dd1 on mat leave with dd2 and hardly noticed the effort. I was there all the time anyway, it was just part of the job.
So part of the Thing of being a WOHM is fitting everything in. Life is an intricate mosaic in which no sliver of time, however weirdly shaped and pointy at one end, can be left unused, without something wedged into it. So that is draining in itself - not just the doing, but the mental puzzle of completing the mosaic so that every 24 hours somehow holds together with all the shards fitted in and staying in place.
Similarly, when I was on maternity leave it was bloody hard work but at least I could zone out when the dcs finally went to sleep. (Also - another point about the CM - with both my dcs, the children I handed over to them were cheerful, communicative 10 - 12 months' olds, happily in a routine, and eating a wide range of normal, easily prepared foods - the job of turning a mewling alien who lives on the breast and screams inexplicably and randomly into a child with a bed time, nap times, and meal times, was mine, all mine, lucky me) (actualy I take that back, it was probably more that the job was living with the alien until it turned into that child)
You may pick up that I keep saying WOHM and not WOHP. It's a gross generalisation but dads just don't do as much, even when they are officially SAHP. I am kind of embittered right now but I still remember being really upset on my first day back after maternity leave when I came home and there was no dinner for me and nothing for me to eat. I had made dinner for the 4 of us every night when I was on maternity leave, starting with a 1 week old baby. Every single night there was something even if it was Fruits of the Freezer and we sat down and ate it at the table. The first day I went back to work and left the dcs with their new SAHD he texted me on the train with a picture of the beautiful feta and tomato tart he had made. I had no idea that in the 20 minutes it would take me to get home, he and the dcs were going to demolish THE LOT. Every scrap. That picture was cruel - showing off "look I can cook" (oh you mean you can throw food on a sheet of bought pastry, well, fair enough, you have a toddler running rampage and a baby entering evil hour, I get it) but not saving me ONE PIECE?