It does happen, I have send more wood and steel into the trash than most of you will ever see.
There comes a point however when skill and confidence meet and you can do great work. I have had many projects where there was no possibility of backup. I made a blade for Mark at itsaburl, out of a piece of meteorite he sent me. I had never seen another piece like it(size shape type pattern) and I will probably never see another. There were no backups and no room to screw up. There is a point where you can't afford to be nervous, because you will sabotage yourself. Now maybe you are not quite there with your skill, and you need more practice.
Think about this, I make gold/silver mokume, somtimes with several thousand $$$ worth of materials. I really can't afford to screw up, and I don't.
(Oh and by the way I make damascus petty blades)