Even better: stop entirely! I started down the vegan road as a trial run: "one month, then we'll see." I doubted that I could deny my need for cheese for a whole month. As it turns out, I could. And I felt so awesome, that I never went back. I learned to cook with delicious things I'd never tried before (e.g. nutritional yeast), found yummy cheese substitutes, and even learned to make my own cheese using soy and nut milks and age-old techniques. I stopped feeling like taking a nap in the middle of the day, and my energy level went way up. My health got better almost immediately (more on that some other time), and my mood even improved. The best part: one of my daily life habits, eating, was no longer in conflict with my moral convictions. I was hooked.
"Eating healthy" is a common New Year's resolution - but it's also conveniently vague and noncommittal. For a more specific, more beneficial plan that you can actually stick to, try 30 days of veganism. Apparently, there's even a movement surrounding this idea of trying out a vegan January: Veganuary. (I just found this out right now on Google, and don't ask me how to pronounce that.)
What is my New Year's resolution? Read (or listen to) 40 books this year and start swimming laps (again).