Those who are long-term married, what do you think is the most important thing?

Married 24 years.

The most important thing is compromise. To let go of your ego; first with your wife, and then with children.

Sooner we start to say YES, better is our quality of life. People hate to hear NO. There is no such thing as "constructive feedback" in relationship :) That is an HR nonsense they say at work...