Wow, that's a hard one. I personally set my goals extremely high and then try to reach intermediate goals in route. I would like to say I would consider myself a success when I can play like Gary Moore... One of my favorite guitarist. However that wouldn't be completely true.

I set that goal which.. for me.. I think would be almost unattainable. So the truth is I could still consider myself successful even if I never play as well as Gary. But when would I become successful? I think a hundred different times along my path to my goal. I was successful when I finished GF1 and will be successful when I complete GF2 and then again after the blues course etc...

But so far I think my greatest success was making the decision to learn how to play.