"How few there are who have courage enough to own their own faults, or resolution enough to mend them." Benjamin Franklin
Endurance athletes tend to be a highly motivated group of people who typically don't make New Year's Resolutions. That said, very few of us have reached the pinnacle of our athletic potential and in turn are constantly searching for that thing that will help us get to the next level. As you sketch out your schedule and write down your goals, consider resolving to make these three things part of your plan.
Resolution #1: Commit to strength training year round.
Many endurance athletes see time spent in the gym as time wasted. Yet strength training has tremendous benefits for the endurance athlete including increased hardiness, reduced recovery time, and improvement in strength endurance. During the off-season make an effort to include three days a week of total body strength training. Once your sport-specific training volume picks up, reduce that (if you'd like) to twice weekly. The key to optimizing the benefits is doing it year round.
Resolution #2: Add a pre-workout mobility routine.
The most overlooked and underappreciated element of any fitness plan is mobility. Perhaps because it's the easiest thing to do physically it's often skipped in favor of more vigorous activities. The repetitive motion and impact nature of running sometimes results in issues such as IT-Band and piriformis syndrome when the associated soft-tissues are not at their optimal length and tension. An easy way to work on correcting these length/tension issues is to discipline yourself to include mobility work prior to your more vigorous activities (ie. strength or endurance training).
Resolution #3: Make recovery practices a priority.
The most powerful variable of any training plan is consistency. When training units are consistently executed as planned, improvements in performance are possible. In order for an athlete to give their full effort to a training unit they must feel recovered from the previous workout. This recovery requires planning and execution. The most consequential recovery practices include rejuvenating sleep, hydration, and nutrition.
A resolution without an implementation plan is simply a thought. Begin to adopt these effective training strategies by first writing them in your training plan or journal. And with some routine practice they'll become second nature.