everybody is scared about it in the beginning. the thing i learned is that it's like an entirely different game when you shoot low. completely different than shooting a high number. It's like the difference between baseball and croquet - both involve a ball and a stick that hits the ball, but other than that, there's nothing the same at all.
after you've shot low a couple of times and see how the cat won't plummet down, but instead has this really great, flat cycle, it becomes really attractive, and then you WANT the low numbers to shoot.
in a lot of ways, shooting high numbers has more "risk" to it than shooting low. the cat can get a lot of speed going down from a high number, but shooting low there isn't very far to "fall." and typically, they don't.
the lower the number is that you shoot (above 50ish), the less the cat's BGs are likely to move. if you shoot a 75, she might only move 15 points or 20 points in the whole day. When you shoot 500, she might move 300 or 400 points.
maybe if you think of it that way, it will give you courage. She's going to continue giving you the opportunity, so just think about it, and like dyana said, if you post here asking for someone to stay with you when you shoot low, we will. whoever helps you make the decision to shoot will either stay with you or will find someone else who is experienced to keep checking on you.
you won't have to do it alone.