Smartwatches, rings, and fitness trackers have completely transformed how we work out. But while they are incredible pieces of technology, the most powerful tool you bring to the gym isn't on your wrist—it's between your ears. When you sync your wearable tech with basic sports psychology, you stop being a slave to the data and start using it to unlock serious mental gains. Here is how your watch changes your brain during a workout, and how to use it to your advantage.