I'm going to put on my editor's cap for a moment — if you don't mind my using such a??clich??d expression — and mention something that editors really, really want from their freelancers: to stay informed.
Yes, of course they want quality writing. On deadline. Within the requested word count. About the subject discussed, within the guidelines discussed.
However, editors will ??forgive a multitude of sins if you just take the time to keep them informed. Did you find out that the entire premise of your article has turned out to be completely wrong? Tell the editor, and suggest an alternative theme, or subject, or twist. ??Has your main interviewee gone on vacation for a week? Email your editor and ask for a bit more time on that deadline.??Has your kid come down with the latest nursery school plague, and you won't be able to do any work for the next few days? Again, email to ask for an extension if it's a long-term piece, and??if the article is really time sensitive and/or you haven't really started work on it, offer to let the editor find somebody else.??
In other words, let your editor know what is happening with the article. He or she is human (really!) and will understand that life occasionally gets in the way of a deadline. But if you don't give notice ahead of time, or stop answering phone calls or emails because you're ashamed that you haven't hit the deadline, you're a lot less likely to get another assignment once that one is done.