When I first began to GM, I'd be frustrated. I wanted everything to go so smoothly, and I worked hard at it--at keeping the pacing of the game going, enabling the player to drive the plot, and keeping the rules the heck out of the way unless needed. Inevitably, of course, there would delays in the game, slow points, and times when I had to break out the rule book to clarify a point or because I couldn't remember how it worked (beyond the point where fiat would suffice). Some of the actions that transpired were ludicrous. And though the players would say they had a good time, I'd feel like the night was a bit of a disappointment. I wanted perfection--I wanted games that sounded like all the stories I'd heard of amazing sessions from veteran GMs.
But a few months down the road, when we had wrapped up our campaign--I realized something. When we discussed the game, we didn't discuss or even seem to take into account those delays, the slow points, or the loose ends that to me stuck out like a sore thumb. No, we were talking about all the other stuff that'd happened! As they talked, I noticed so many of the flaws that were so glaring to me weren't coming up--and it was sounding a lot more like one of those "polished" sessions I've heard of from other GM's and gaming groups. It was the overall impression that was important, and in that, we had succeeded in having a good time, and ending up with a pretty good yarn while we were at it.
Being a Game Master isn't tidy work. There are loose ends, anachronisms, and nonsensical bits aplenty for the critical eye, even in the work of the best of us. And though it never hurts to strive to be the best DM/GM/CK/Referee you can be, the overall body of work is much more important than a few typos and incomplete thoughts that may have transpired. By and large, the players are going to want some whoppers to tell at the gaming store cash register--and that means they're going to highlight what was awesome and tidy up or straighten out that which wasn't.
It remains one of the best lessons I've learned as a GM: a) Don't worry too much about the mess around the edges--it'll get cleaned up in the telling, and b) Gamers are great at retconning.