The world at large understands this popular phrase to mean that since you only live once, do what you please, and live it up! For marriage, You Only Live Once means make the most of the life you have, the most of the moments, the most out of your relationships, especially your relationship with your husband. Take control of your life and you can improve almost all situations.
We all have a violin we are born with - the question is how big is your violin? What are you doing to make your violin smaller? What are you doing to make the only life you have better -- because YOLO!