I'm speaking from experience when I say it is often difficult to get things right the first time. I'm sure many would shake their heads and boast "I do," but some don't. I am one of them. To give you some personal background, I have not yet released any maps myself. I'm in the progress of making a little Half-Life Single Player episode entitled Scorched Earth. I made my first level fairly quickly and thought "Genius." Then, while over at the Valve ERC (Link: www.valve-erc.com)
for some tutorials, I was looking through the news archives and found a link to a Half-Life MOD named Nightwatch. I clicked, I looked, I cried.
Nightwatch's level designers are far more experienced than myself and many other fellow mapping newbies, but that shouldn't put you off, just as it didn't put me off... much. I might not be able to make maps that match the standards of the Nightwatch team, Valve, or any other semi-professional MOD developers, but I can have a damn good go.
So what's my point? The point is that if you think your creation looks appalling, do it again. You don't actually have to start from scratch, but basically tear it out and rebuild it with a more careful eye for detail and construction. Think why it doesn't seem very good. I felt that my map looked way too bland and basic. I'm not saying that anything below the standard of a Valve map isn't good enough, but I think that rebuilding something can produce a much better result than the first time around. Remember, map making isn't like painting, where once the brush hits the canvas you're stuck with it. Worldcraft (or Hammer) allows us to put down the brush, then twist it, turn it and break it in half all we want. And if it's no good, we can undo it all. Yay.
For a good example of the benefits of a second attempt, just look at the two screens below of the room where you collect the HEV suit in Scorched Earth.
Picture this: You build a level (Single Player, Deathmatch, whatever) and you think it looks great. Then you pay a trip to a mod website and look at some of their screen shots. "Goodness me," you think (in not so many words), "that looks much better than mine. Much, much better." Granted, it probably does, but it doesn't mean you have to leave your ex-masterpiece in its current state.