One of the ways marriage [1] can make things easier is by allowing you to divide jobs, freeing each other up for other things. For example, here are some things each of us are responsible for:

• Jeff: Lily's bedtime
• Julia: Anna's bedtime
• Both: cooking
• Jeff: fixing house things
• Jeff: stocking non-perishable food
• Jeff: tidying after the kids are asleep
• Julia: laundry
• Julia: organization for kids stuff
• Julia: kids clothes
• Both: general parenting, childcare
• Jeff: finances, taxes
• Julia: finding long-term childcare, coordinating with au pair
• Both: full time work

The traditional way to handle this is with a gendered breakdown: each person has a gender role, tasks are male or female. This has some advantages:

• More efficient preparation: from a young age each person can be learning how to do their jobs.

• Lower coordination costs: both people know which tasks are whose without needing to divide them explicitly.

• Purposefulness: some people find great satisfaction in having a socially determined role, knowing its boundaries, and filling it well.

But it also has major disadvantages:

• Unfair division: there's not much force keeping the roles an even split, so it's common for the wife to do more work.

• Inefficient division: people's interests and abilities won't align exactly with the standard roles, and can be significantly off.

• Non-heterosexuality: not everyone wants to be or will be in a male-female couple.

Julia and I have ended up with a division that is closer to the traditional one than if you assigned tasks by chance (me doing maintenance; Julia doing laundry) but not entirely (sharing cooking and parenting). I don't know any roles we could shift around that would improve our joint happiness (or we would have done that) but it's hard to tell since we can't perfectly communicate.

Divisions seem to work best when they allow the other person not to have to think about the work involved at all, but this makes it easy to end up with unfair splits. One person could be doing much more work than the other without this being apparent to either. Worse, both people are more aware of the work that they're doing than the work the other person does, which can lead to feeling like you're doing more regardless of whether you actually are. I think time tracking can help a lot here, but you also need to be careful about dividing tasks that are mostly mental burden without a corresponding amount of time (keeping track of birthdays, appointments, etc).

[1] Marriage in particular, because it lets you plan long term divisions. A lot of this is still relevant for shorter term stuff, but then it makes sense to have more shared spheres so you're in a better position once you're not together anymore.