Support each other's goals.
To grow together, you also need to grow individually. So when you whip up that list of resolutions, be sure to share them with each other.
By articulating your hopes and goals for the year, you allow your partner to be support and assist you in making them a reality. Whether it's hitting the gym more, or hustling up the ladder at work, you can push one another, help maintain your motivation throughout the year, and keep each other's eyes fixated on the prize.
Bonus: When either of you achieve your desired goal, it will feel like a mutual victory.