Practice makes perfect - each quilt you make will have "mistakes" in it - don't worry about it. People will only notice if you point out the areas in question. Most people look at the big picture and never notice the little glitches. In one class I took the instructor had an award winning quilt - until she pointed out an error no one, even the judges, noticed that one area of the quilt was pieced incorrectly. It happens to all of us.