I remember experiencing the same thing as you are doing now, but you just have to jump in & do it or you never will!
I did think the sandwiches were a waste of material, so I bought some (what I call) cheaters cloth (pre-printed design in quilt pattern) and added batting and backing and practiced to my hearts content and until I had the size stitches and curves in stippling down pat. When I was finished I had a very usable quilt which was kept in the car and used many times on picnics, at ball games etc. Still in use today, thirty yrs later.