How can i get over my fear of doing a back handspring?

So..im in gymnastics and i can do one on the trampoline with a spot perfectly and my coach says that i can do it by myself. I have a tramp at home and ive been practicing a lot but i still cant do it. I can do a back drop and ive been doing those, then ive been doing a back drop and flipping back (still doesnt help), and i have also been doing the first part of a back handspring but then landing on my back. I dont know why im scared to one but whenever i try i cant do it. Please help me, ive been trying to do one by myself for about a year now. I feel so stupid. so pleaseeee help me and i will vote best answer. thanks