First of all, you're not a failure! These things happen and you just need to work out how to handle this situation.
I really loved watching the Cesar Millan DVDS .. when I got my new puppy 1 month ago, I put him on a lead in the house and we wondered all around the house. I would let him go up to things and the minute he touched anything off-limit (like wires, shoes etc.) I would make a correction - which would be a slight tug at the collar and make a noise. I kept re-iterating that .. and he eventually learned which things were ok to touch and which things were not. It only took 2 days, and now, he knows to go to his toy for what he wants. Also lots of exercise!
Hope that helps and your puppy is teething, maybe get a large bone and one of those toys that you can stuff with food.