"Control is for beginners" - that is probably the best quote ever (see the HBR article for more info - thanks, Deb Mills-Scofiel for that!). And it is so true. If we wait for perfection in business - or the exact right thing to do - we get nothing done and become a bottleneck. AT&T stopped being innovative because of it. You can't get to perfection unless you put something out there, see what happens, and make changes to make it better (sounds a little like Agile, huh?).
One my teachers recently told me that we are all perfect - and this applies also to control and to Agile and improv. Whatever you do in this time and space is the right thing to do. You can always make adjustments if you learn more about something in the future. But what we do now is just fine.
The next time you work on a project - keep that in mind. What you do now is just fine. If improv musicians and dancers didn't think that way - they would never perform, never try something new, never create something great.
Take it one step further, we wouldn't have flight, lightbulbs, the Internet, x-rays if someone didn't iterate. Iteration is the mother of invention.