Specificity Training: The principle that states that what you do in the gym should be specific to your sport and the outcome you desire.
To put it simply, a runner should run, a swimmer should swim, and a cyclist should cycle. But we're not idiots and we know that. So let's take it a step further.
I know many runners who like to train on the treadmill. But if you are training for an outdoor race, it makes sense to take your workouts outside, too.
Get out in the terrain you plan to race on. If the course has hills, run some hills. If it's on the trail, get your cutie patootie out on the trail!
Do you dream of one day being able to perform pull ups? Then you better practice them. And you should also have a strength training plan that includes plenty of exercises to strengthen your back and shoulders. Grab some dumbbells, hit up the cable machine, and get to work. Those lats aren't going to get swole themselves.
Are there any areas in your training in which you would benefit from more specificity?