My first had poor sleep due to bf (their bodies process breast milk quicker, its just biology innit), later reflux. I think I accepted it when he was tiny, just as pp said, limit your own expectations.
What I definitely struggled with, with regard to sleep deprivation, was that my now ex never once got up in the night. Not once. With either of my dc. Blamed my insistance on bf-ing, didn't change a nappy, asked if he could do anything to help, never 'allowed' me to have a lie-in. He worked full time and decreed that his time outside the office was his off-duty time, he could eat, drink and do whatever he wanted. That absolute resentment eventually transferred to the babies and made me hate those dark hours, the stupidly early starts to the day.
With my new dp I'd have another baby in a heartbeat as I know his attitude would be so so different.
Babies have 2 parents. Even if one of them is doing all the milk production, the other absolutely needs to step up at least as much to allow mum to recover, snatch up some sleep and realise that stepping out of the door at 8am to 6pm is a walk in the park compared to looking after a newborn 24/7