Sometimes the words you need, when you need them fail to come to mind.
What do you say, when you know that something needs to be said, but you can't think of what it is? That yearning to express yourself that bubbles up until finally you can no longer deny that something must be said stalls when you realize that you have no idea what it is that you need to say. Instead you wish you could lay your hands on the person you're trying to communicate with and transfer the emotions that are preventing the words from being formed. Only then will they understand what it is you need them to hear-which is really only the need for them to feel how you feel, for them to really get it.