To me, when you're building something that hasn't existed previously, there are a series of steps what you're building goes through:
- Ok - what ever you're building is "Ok", meaning it solves the problem for which you're building a solution.
- Better - The thing you've built solved the problem and now you've improved it.
- Well - You thing does the job well. For all practical purposes, that means you show it to people without apologizing.
- Good - People are impressed enough with what you've built that they show it to other people and say it's good.
There are levels above good, but they are refinements that are distinct without necessarily being different.
Now, if you are managing something, it already exists. Hopefully it's "Good", more likely it's "Ok" and could be made "better". The import point is that it's purpose for existing has already been identified.
In this case, managing something is about refinement and continuity. Maybe there are parts that are replaced, tuned or refined, but continuity is the defining characteristic.
Maybe it can be better thought of like this: Building is about creation, managing is about continuing.