Back handspring help?

sooo since i was like 8 all my coaches have been saying that i can do a backhandspring by myself. and i would do them in the gym if my coaches would put their arm out- i wouldnt even need a spot but i refused to do it by myself. Now, im 14, have quit gymnastics and still cant do a backhandspring. i went for tumbling classes last week and within the first 15 minutes of doing backhandsprings, the coach asked if i could do them by myself. i KNOW that i can, but why wont i?