This is not exactly an answer for after they are married, but if there is anything I could say to any young couple BEFORE it's too late:
Take a hard look at any "little" thing that irritates you about the person you are considering spending your life with and ask yourself how much of an annoyance that would be if it happened several times a week and got steadily worse. It will. Does he/she tend to boast? Interrupt? Tease in a hurtful way? Chew fingernails? Say nasty things about your friends and family? Buy roses when you said you like chocolate? Drink excessively (even once is a red flag if you don't like it!)? Insist on the movie he/she wants to see and never the one you'd like? Criticize anything about you in a painful way? Ask where you want to eat out and then tell you why it's no good? Try to control what you wear, what you buy, and where you go and with whom? Run issues into the ground, long after you want to move on?
Just please take off the rose-colored glasses and be sure you see the bad side of this person as realistically as possible. Everyone has faults, the decision is what kind of faults you might find intolerable.