Music to me, is like temporarily living in an entirely different world. When I really listen to it and not have it on for background that is. I can get chills, become emotional, feel pure joy, replenish my energy, or release energy when listening to music, depending on what song I listen to. When I have to deal with emotions alone, like anger or sadness, music helps me deal with them. I'm what you could call an audiophile. The better the music quality, the better for me. And I always try to get the best quality both from the music file and from my headphones or midi tower.
That being said, to let music define who you are is kinda stupid, imo. Music is only part of life, not the be all end all.