haha good to hear you are feeling more inclined to learn mathematics! Math has lots of applications in the real world, but fundamentally it is just a mental exercise of logic. Chess or other similar board games are other good examples of mental workouts, which have indirect benefits to one's mental well being in the same way that lifting heavy rocks (aka physical exercise) has to one's physical well being. 

Regarding even and odd functions, unless you are dealing with modeling electromagnetic waves, I'm not sure how they can help you directly. But in terms of the underlying logic, it is just an exercise in pattern recognition, which can indirectly help you notice patterns in your everyday social or work setting.