Ironic this topic came up...

I practiced clipping in and out between a door frame inside my house (same concept as between two cars). I found the motion easier than many people talked about and never fell once...that is, until today! I just forgot both feet were clipped in when I came to a stop Good thing there weren't any cars coming up behind me at the time

It sounds like you need more advice. If you have a yard that is rideable, get used to the pedals while riding in the grass. Go to a school yard if you don't have a suitable yard. Doesn't scuff you up if you fall. Just clip in and pedal in your lowest gear and practice stopping and starting. Relieves the fear a bit. I trained both of my progeny like that and they still have unscuffed knees.

Wished I had gotten all this advice before I went out on Memorial day and wrecked and in the meantime broke the arm. Thought I had practiced enough, but I guess not.