My husband and I served in a marriage ministry for 5 years. The most important thing we learned was that our relationship to God was more important that our relationship to each other.
But that the closer we grew towards the Lord the closer we grew towards each other.
We also learned that we as a couple were more important than the kids. But the stronger our love grew, the more it radiated towards the children, the more we as a family grew tighter.
Before my son was married he said "Mom, I want a marriage like yours." That phrase is more precious to me that diamonds.
This is the advise I gave my son before he and his wife were married was that
love is a decision. I decide to love my husband everyday. Some days, it's a very easy decision to make.
Other days it's a very contemplative thought process 
But I decide to love my husband daily.
It's like our walk with the Lord, I suppose.
We've only been married 15 years. It will be 16 on April 1st.