writing techniques

It seems I write best when I'm angry or debating a point, so I've observed, or when I'm asked for advice on a very specific question. There's no hesitation - the words just flow; my words are concise, sharp, and sometimes deadly - like an automatic weapon. Still, at other times, when no challenge is presented in front of me, I yearn for the right words to express myself fluidly, oftentimes feeling defenseless against the blank sheet of terrorizing paper in front of me.