I'm currently adding onto an existing story of mine in order to increase the word count. This is not a problem for me, since I can always say more:) My problem is usually knowing when to shut up. In writing I always try to ask myself, "Does the reader really need to know this?" and "Would they care?" I'll never forget the time I read a very well known fantasy author's book and got a three page description of a dirt road. (Really could have done without that.)
As it turns out, I'm finding things to add in, bits of extra description and conversation that are really bringing the story to life more and more. I was already very pleased with it, and now I love it more.
I'm glad I decided to take someone's advice and make these additions, because they are really improving my story, not just "adding words," which I would never do. The way I see it, if you can tell the same story without including something, then perhaps it doesn't need to be there. I'm probably my worst critic and I'm certainly my harshest editor.
The point of this rambling message is that I'm really enjoying getting to know these characters again, and embellishing upon their lives a bit more. Once this story makes it to the public, I hope my readers feel the same.