My writing students typically have a lot of trouble with word limits. They spew words on the page, and when they find out their manuscript is too long they say, "I just don't know what to cut!" But it isn't a matter of cutting as much as replacing; they need to take the time to find the one strong word that can replace three weak ones.
I think computers make it too easy to spew words. You do it because you know you don't have to worry about how you'll clean it up later. When writers used typewriters it was an ordeal to change a word (often you ended up retyping the page), and revising a manuscript meant retyping the entire thing, so you made sure that every word was perfect before you pressed those keys.
While revising a novel recently, I spent an hour finding exactly the right word to replace a word my agent didn't like. An hour! But I really did need to choose the perfect word, because it was part of the opening sentence of the book. (You know what they say about first impressions.)
Some of my students have really strong aversions to revising anything. One came to me with a manuscript that was about 100,000 words too long and said, "I'm not cutting a word, so don't even ask me to." (What editor would want to work with someone like that?) I told the guy, "Don't worry about it. My edits are always suggestions, not mandates. You don't actually have to make any of the changes I recommend." In other words, I marked up the manuscript anyway, showing him what he could (should!) cut, and left it up to him to reject or accept the fact that his manuscript would be better off shorter. In the end, after much internal struggle, he ended up cutting about 50,000 words, unable to part with a weak subplot that would have taken care of the other 50,000.
Another writer who won't revise (but isn't a student of mine) is in the process of falling for a scam. He wants to believe his novel (a first draft) is perfect as-is, and he's found someone happy to tell him so. She has a website offering to help writers with their novels, but she's vague about her credits. "I've created content for ABC, HBO, and other networks," she says. No specifics about credits, no mention of belonging to the Writer's Guild. What does "content" mean, exactly? And why offer help to novelists if you write for television? It doesn't make sense -- but the revision-resistant writer sent her his manuscript anyway, paying her several hundred dollars to read it, and she praised it in glowing terms. Then she said something like, "Your novel just needs a little tweaking, a few minor word changes here and there. I can help you with it, for an additional fee." Next she'll probably offer to help him submit it, for a fee.
(There's an interesting article about a similar scam at http://www.razorsedgepublishing.com/publisherspick.htm)
It's tempting to think your writing is really that good -- and of course, sometimes it is. But it's better to have several people tell you that than just one, and to get feedback from individuals who have nothing to gain or lose by telling you one thing or another. With my own manuscripts, I get feedback from my daughter, my husband, a good friend, and my agents. (I now have two agents, plus my agency encourages everybody in the office to read and comment on agency-represented novels.) And if anyone tells you a first draft is "perfect," doubt them. I've never yet come across a novel that didn't improve with multiple revisions.
And now I'm tempted to revise this post, because I've found myself talking about revisions (again) when I started off talking about word limits. But instead I'll just give a final word of advice on word count. If you're good at revising, go ahead and spew while writing your first draft, with the awareness that you'll have to cut a lot of words later. If you hate revising, take the time while writing that first draft to choose each word carefully, tracking your word-count progress as you go to ensure that you won't have to cut a bunch of material later. But either way, know that at least one full revision of your manuscript will always be necessary, and usually many more revisions as well. (The typical for me is eleven drafts, which is why I'm tickled that there's a good book on writing called The Eleventh Draft.)
So until next time, let me wish you not only "Happy Writing!" but "Happy Revising!"