The whole 'ick' thing, which can happen at any time, over anything, and apparently once you have it, that's it. I'd like to think most reasonable people wouldn't leave after years because they didn't like your new haircut, but then we're always hearing 'You can leave any relationship you want, for any reason'.
You've then got to have the right balance of everything. If your partner/husband wants to go out 4,5,6 evenings a week, You've just got to make your own life and deal with that. You can't decide how much time you get to spend together.
You've got to be very chill about 99% of things, be cool, don't be dramatic because pepple don't like dealing with others' emotions.
You've got to earn enough money to afford that dream house they want in the best area, otherwise you 'don't want the same things in life' but you've also got to have extra money for adventures, travel, looking after the way you look, keeping things exciting, holidays without them to 'have your own life'.
I'm probably over-exaggerating, I know people don't expect perfection but I feel like there are these very high standards to meet at all times.