Many of us have similar experiences, where the former partner is essentially just a large child unable (or unwilling) to step up. There's no easy answer and we all have to find our own ways to get through. I was fortunate in that even when I was totally exhausted (getting maybe two hours sleep a night if I was lucky, plus running a startup) I didn't want anything other than to have my children with me. But I was 20+ years younger back then - today a similar situation would likely be unsustainable. For me, part of coping was to consciously look for tiny moments of magic each day, like seeing my daughter sitting on the stairs playing with a toy as the sunlight streamed in from the window behind her and framed her head in gold, or watching her carefully measure water from the tap first into a large spoon and then into a smaller spoon. Or seeing the look of concentration on my son's face as he carefully painted a picture, or feeling his hand wrap around my finger. These were tiny pick-me-ups that brought joy and sustained me. I hope you're able to relish similar moments and that they help ease the burden just a little.