As a writer, I find myself facing this terrifying foe all too often. My story line is solid, but I just can't find the words to express what I want to say. The more I try to force it, the bigger the block becomes until, soon, I can't write anything at all.
For those of us who need to write, this is a horrifying scenario indeed. Our life's blood is literally tied into our ability to jot down our thoughts and dreams, and when we cannot, life seems somewhat dull in comparison. The fact that we cannot make the words pour out brings our very nature to a standstill.
If you find yourself in this situation, do what I do. WALK AWAY. Put the manuscript down and just leave it for a bit. I know it is hard, and the writer in your is compelled to sit and try to bring it out, but the fact is, anything you try to write will sound forced and dull. When I come back to my manuscript, hours or days later, I am always able to find that spring of creativity welling up within me and bursting through.
It is not an easy life being a writer. Nor is it nearly as glamorous as everyone seems to think. If you want to make it in this business, you have to know when to push and when to sit back. When I was a child, my brother gave me an analogy that to this day rings true. He had a tangle in some thread, and I was trying to help him work it out. He said to me, "Never pull. Like a relationship, if you pull, it will break." Funnily enough, this doesn't just apply to relationships, but to many areas of our lives. So, I will not pull. I will just work through my knot until the tangle is released.