Everything already said, but especially laugh together. In just over 29 years, there has not been one day that my DH hasn't made me laugh. A sense of hunour is invaluable.
And NEVER(yes I meant to yell) go to bed mad at one another. Not because one of you might pass away, as stated earlier, but because if you don't work it out, it will seem even more insurmountable in the morning.
And good luck for a long and happy married life together.