Scared of doing a backdrop without a mat on the trampoline?

[Lilly-Mai <3]

I can do a backdrop perfectly when I know the mat is there or I know it is coming in but when my instructer says it might not be coming in i panic and either cant do it or do it subconciously badly so the mat comes in. I just get too scared and i have being doing backdrops for ages. I can even do front summersaults now with no fear but when it comes to backdrops with no mat na ah. Any advice?????
I am 14 if that helps!
I have a 12 foot trampoline to practice on!