Now that you are relaxed imagine forcing that rubberband even furthur from you. You should feel a strain in your core chakra like a tightness. Try molding it around objects pullit in and back out like a wave, this will calm you even furthur. (by this point my palms and feet where hot so this is normal on the first try)
Now pull it back in close to you for the visualization exercise. You should think of a place you love. try a comfort place first. Try to remember every detail and actually see it in your minds eye. now focus on what all of your senses experience in this place. Like the smell of grandma baking cookies, flowers in a garden, sea water at a beach. now trap that memory and keep it there. You can always go back to that place if you retain it.
Now just relax and pull the rubberband back inside you. By this time I was tired so I fell asleep but you can play around with many other visions or your shield if you wish