I want to encourage you to keep trying, it takes time to be good at any specialty.
First take your time in searching for a vein, make sure that it is straight, long and juicy, you can feel a bounce when palpated, don't be in a hurry to stick.
Secondly, make sure that you are well seated and comfortable where you are in relation to the vein. Then make sure the vein is engorged with the tightening of the tourniquet, you may stabilize it with youl eft 2nd or 3rd finger and the thumb if you're right handed, since some veins move. With the bevel up insert at 10 to 15 degrees, and extend press on the safety button and the needle will be sucked back out of the cannula. Be sure you understand the equipments you are using, use a smaller guage needle like a 24g for a thin and short veins and about 22guage for a big vein. Most of all I like your attitude, you can do it !!!!!!!!!!