When I try to sing music that I find especially beautiful, my voice cracks and I start crying... how can I emotionally detach myself just enough? Getting a story across when I sing is probably my first priority, even above technique.  I usually don't have a problem singing evocative lyrics, even when I deeply relate to them; however, when I run across melodies that strike an emotional chord with me, I can't keep it together.  I'm somewhat good at "blacking out" emotionally, so I usually just kind of drift away while I sing those parts, but I'm sure it's pretty obvious to listeners.  

What are some ways I can find a happy balance between being too emotional and ruining the song and just completely stepping out, emotionally?  Given that it has no correlation to the lyrics, it's sometimes pretty disrupting.  