Its all part of a learning curve mate. Don't give up. Don't think of it as failure or a waste. You learn more through failure than you do through success. Keep saving your work, and try not to just 'save', try to save in increments so you can go back and try things again or a different way.

Good luck.

PS. The poly dog tutorial was amazing for me. I watched every section twice before even attempting anything, and because of that it all made a little more sense as i was doing it.