The best single predictor of a long and happy marriage is that both partners are kind and emotionally generous to each other, according to research from the Gottman Institute.
Do you treat eachother with consideration, versus being frequently critical and biting?
Do you tend to see the good in your partner and want to increase his happineess?
Do you appreciate and value your spouse?
Do you make joint decisions and share domestic duties?
All of these have been found to be extremely helpful in having a satisfying and happy marriage.