Maintain respect for your partner as their own individual person who has chosen to team up with you on this exciting journey. I mean this as opposed to viewing your spouse as a work-in-progress; something to be molded, improved, and changed to suit your fantasies.
First, and foremost, always remember that your partner is his/her own person. They can't read your mind. They will make mistakes, and as long as they are honest mistakes you can forgive them. Realize that you, yes even you, will make mistakes. Learn to forgive yourself. There will be times when you can't stand each other. The best thing is to realize how much you love and need each other, and you can weather any storm.
Step outside the day-to-day drudgery and look at your partner as if you are crushing on them and wishing to be with them, as you once did. Now, if you are looking over at a chubby hubby picking his nose you may want to choose another time to practice this one. Anyhoo, it's good to remember the qualities that attracted us initially and to praise said attributes thus encouraging the partner to display them more often. Sometimes I think people in long-term relationships feel that they are just fulfilling a role and not being honored for the unique individual that they are. This can make outside affection and attention all the more desirable.
Imagine yourself broke and miserable -- that's what divorce will do for a marriage. Hey, sticks are always stronger motivators than carrots, even if you're using the carrots creatively in the bedroom. I'm not joking!