Once a week, for a token and minimal investment of 5 to 15 minutes no matter your current choice of sport, practice your other sport. For example, if you're a football player, grab a bat and take 50 swings at a thrown or pitched ball, or hit off a tee. Besides the obvious improvement in skills, you take the necessary step away from the 'new' and 'unfamiliar' act of swinging the bat, and take the essential step toward your body and mindset being in a habitual state of comfort with swinging, as an example.
Be constant, be consistent, be competent. Even if you limit yourself to a few minutes a week, the long term benefits will amaze. Be constant, and be great!