In the first three weeks with my first, we sort of broke the day up into shifts. There was the evening feeding, the night feeding, and the morning and day feeding. If one took the night feed, then the other took the next shift and so on. The times were changeable, we had an unspoken agreement that you went for as long as you could, then swapped.
When he went back to work I did the night feeds. He did the last evening feed. We took turns having a lie in at the weekend, and the one who got the lie in did the night feeds.
I felt it was important he got a good sleep because he was up early and in doing a manual job. I did get resentful sometimes, I was pretty tired, however I did try to go on as normal in life, going to bed later and doing a lot more than I probably should have in the days.
I was on my own with my second, single mum. We breastfed and I had a toddler to be responsible for. For the first three or so weeks, I went to bed at the same time my toddler did, and got up when he did, roughly 7pm to 7am. My DD fed several times a night. I co-slept with her when I could, or had the moses basket next to me on the bed when I couldn't. I breastfed lying on my side curled up around my baby, and dozed while she fed. I kept nappies, wipes, changes of clothes and the likes on my windowledge right next to me in hands reach. I never got out of bed. I never felt resentful.
Sometimes having someone around who could help is a lot harder than just doing it.