It also helps to consciously work at developing the skills you will need to be successful as a couple.
Communication, for example. How to listen well. How to be honest together. How to avoid criticising. How to resolve arguments without tearing each other apart. Staying focused on solving the problem together, knowing when to take a break, and learning to forgive and apologise.
And you need to get to know one another well! Few couples do. Stuff like favourite foods, habits, and whatever it is you both worry about.
Hopefully, you will be together for the whole of your lives, so work at keeping fit, controlling your weight and staying attractive. Constantly strive to understand yourself better and improve yourself, and interpret events optimistically. Learn how to manage stress well, so that you are better able to help and support each other when times are hard.
Above all, learn how to please each other sexually, and think of it as your most important duty to one another. Learn how to be tender and adventurous. And set aside enough time for intimacy, no matter how busy life becomes. Because couples who have learned how to touch and kiss confidently, and how to meet each other's physical needs, rarely ever part.
All the best,
Chris