I would say it's like peaks and troughs.
The physical demand on your body is a lot going through pregnancy. I'm 7 mths pp and still get ongoing pelvic pain which I'm still waiting on physio for. I know other friends who have lost bladder control for years or been impacted by post partum anxiety and depression for a long time. So firstly you've no idea how your individual body will react to and recover from pregnancy.
The demand is a huge change, it suddenly becomes difficult to get time to do any of the things that make you feel like YOU. Whereas your other half can do that much easier. I breastfeed and while I love it and feel lucky that I can do it, that definitely increases the intensity. My dh hasn't been able to do a single bedtime or resettle ds if he wakes so I can't go out in the evenings. Which makes seeing friends or going to the gym etc difficult to arrange.
Financially its tough unless you've solid savings or your partners income is enough to live on. We have enough to get by on but we need to be super careful and it leaves very little for non essential spending in order to protect the savings we do have because we want to move.
There's days that are a breeze now and we've a great routine and things go to plan and then there's days where I feel in a complete fog and we don't even get out the door because nothing goes to plan. You work entirely on babies schedule not whatever you've planned and that can be difficult. That can also make it lonely. For eg we're working on weaning and ds is teething so he's not sleeping. He woke every single hour last night and dh was working today so that meant I still had to get up and get on with it even though I was completely exhausted. Days like that I don't always feel safe enough to drive to see anyone even if I really want to.
Not to mention ds had a tongue tie, weight gain was a struggle and he was wild with colic most nights until 5 mths old. I wouldn't change him or anything about him for the world but it's definitely the hardest thing I've ever done and I'd say we've had it fairly easy considering what some mums go through.