I just wrote the most 500 useless piece of crap words I have ever put on paper in my entire lifetime. I did it, because I'm trying to write 500 words a day -- most days, anyway -- this month, so I *had* to do it. But it probably took me an hour.
But I was too disgusted and tired, so I went to bed instead. I just read those 500 words, and you know what? They aren't all that bad after all. There was a clunky phrase or two in there, but for the most part, they got the job done.
How is it that our mood at the time can affect how we perceive our words? I guess the lesson to be learned here is that the important thing is to get the words on the page, every day that you can. And if you have perfectionist tendencies like I do, not to expect that every word and every writing session is going to result in words of gold. Just let it happen and worry about cleaning it up after. And realize that perhaps it's only your perception that makes the writing seem crappy. (Not always, of course!)
So go, WRITE!