I think there's a tendency for writers to be miserly with their words. A good sentence is like found gold; it should be locked away in the vault, and used only at the right time.
It seems like a lot of writers feel they only have a certain number of good words coming to them. This is only natural, perhaps. Good lines seem to fall from heaven, at times, appearing mysteriously on dove-like wings. Here! A gift! Just for you! It's normal to squirrel it away. Save it up. To write only when the really good words come.
Except this can be damaging sometimes. We tiptoe around the precious words, scared to upset them, scared to bring them out in the open where we might lose them. I can't spend this great line in a blog comment, can I? Hardly anyone will see it, and then it will be gone with barely a ripple left behind! No, I shall write something simple in the comment box, and I'll save up this little beauty for some time when I can really use it, sometime when it will really shine.
But I don't think good words work like that. Writing is more like exercise. The more you do, the stronger you get. Your prose is going to get leaner and better. And the more energy you expend, the more energy you'll have. Sort of a paradox. But the more good words you use, the more good words will come to you. Indeed, better words might even come to you. But only if you spend the good words first.
I think this is partly a matter of simple confidence, or rather the balance of confidence against fear. Perhaps it's normal to think "What if the good words stop coming? What if this is it? I shall save this precious sentence..." Writers fear the well running dry.
And I think this depends partly on how we see the words coming to us. Does a muse send in singing telegrams? Well, what if the muse stops? What if we offend that muse, and the muse decides to send down sweet words to your neighbor, Chuck? What if Chuck gets the publishing contract?
I think it can help if you see the writing as work, and the words as a little heavy lifting. Work hard, lift a few more... and each time you'll get a little stronger. Each word you put out there will make you a better writer. Perhaps the change is infinitesmal and invisible. But it's there. It's been worked into the writing muscles. And the effort is cumulative.
No one gets up in the morning one day, without ever training, and goes out to run a marathon. They won't get far. But if the miles have been tracked into the legs every day, every day for months and years, then a marathon might be within reach. The feet have come to know the cement of the road.
So spend your words freely. The road is long, and you need to build up your strength.