First, I believe God created us to be singers. Besides the fact that singing is actually easier on your vocal cords than speaking, too many Scriptures indicate that God's people are to be a singing people.
Second, it gives us a sense of release. For me, singing opens up something that feels bottled up inside me. It's almost like, "how can I NOT sing!"
Third, singing makes my heart engage with my mind. It forces me to think with something more than just the grey matter. Don't get me wrong...grey matter is good...but it's better, more complete when coupled with cardiac muscle.
Sing out loud today...and sing like you mean it!