Ten years is a long time, a dime. As a messenger it's a really long time. Ten frames as a messenger frame builder is a long time. Refitting a carbon rear into your perfectly good steel frame is anarchy. Do it all. There are things you've done and things you haven't. Check 'em off and call it experience. Pay attention and call it knowledge. Learn to do it better next time and call it craft. Hone it slowly over time and you are a master.