"Think about the audience and how much you want them to love the songs you love"
I've always though that the object of the exercise is to think about the song, so that the listener can think about it with you.
Tension, technique, voice production.... all the technicalities of singing are preparation for giving voice - if you have to think about yourself, your listener, big red buses..... anything other than the song, you are not singing, you are going through the motions.
Jim Carroll