My 2nd wife and I were both veterans of 12 step support groups so we were introduced to healthy relationship skills. We expanded on this by reading a few Relationship books and diligently applying the skills and techniques to our marriage so we would not unwittingly repeat the bad behaviors that ruined our 1st marriages.
Of the skills that we used 100% honesty ALL THE TIME did us the most good and paved the way for deep trust, love, respect and loyalty all of which came down to a very affectionate and committed relationship that held steady for around 26 years.
We out lasted most of the couples we knew and were very best friends the whole time. We learned that our love and goodness had to be constant and not done just whenever we felt like it, so our happiness stayed solid all the way through until my wife crossed over a few months back.
We just basically learned from our mistakes in therapy and vowed to do better in our last/current marriage by following a few basic, easy tips and skills we took from books and common sense. We had no kids so that made it possible to avoid much of the stress that most couples face while raising their kids.
She has two grown kids and I have none so we could devote a huge amount of QUALITY time to each other and we did.
Many couples FAIL to be or become best friends
and that alone can make a relationship wonderful and everlasting where there is genuine, loving friendship in the union.
I'd tell any couple to just google: Relationship Skills or Tips and get going learning how to be terrific partners FOR LIFE.