Like I tell my work study's all the time when they screw up (just about every day actually), as long as you learned something from it then it was a worthwhile process.
I'd say, since you have your knife and leather now, just do your best to stop and focus on tooling for a little while. Tell yourself "NO, I have to get better at this" every time you want to go work on some other aspect of leather. I have the same attention problems, but I like to think I've done a fair job at learning how to work around them.
I'm going to send some links your way here in a little bit - hopefully they won't add too much fuel to your fire.