It took H and I a loooong time to adjust (and we still are!) to having a new baby. It was a much bigger adjustment than we ever anticipated.
What it really comes down to is providing support for each other. No relationship is 50/50 100% of the time. A lot of the time it's 70/30, 90/10, etc. When I know H has had a particularly hard day/week at work, I generally don't ask for help with DS. I'd rather call my mom or sister to look after him for a few hours if I need a break, or even call our sitter. It just makes things much more pleasant for everyone.
We've also dramatically lowered our expectation in terms of chores and errands to be accomplished, and do our best to multitask our time (like working out when our favorite TV show is on, or taking DS for walks and counting that as a workout, or running errands together so we get time together as well).