Yes you can press too much. Over pressing can even distort your blocks, especially when there is bias involved. I have been taught a technique where you press your quilt top only after it is all sewn together for perfectly seated blocks. It works amazingly for perfect block joins. Also it is important to press down with the iron for a few seconds and not slide it around. I always use steam, but not starch - this is simply my preference. When I teach I always talk a bit about pressing. I often tell students to "press less".
