Guilt and Morality

How influential is guilt in determining our moral character? The author suggests that guilt "...is such a fundamental moral category that it plays a constitutive role in the ways in which we conceptualize our ethical relations to others. Without experiencing guilt, or at least being able to do so, we would hardly be capable of employing any ethical concepts or judgments. We have to able to acknowledge guilt, to see ourselves as guilty, in order to acknowledge responsibility for our actions." That's obviously a pretty big claim to make. I agree that guilt does play a very big role in our morality, and that the basis for a lot of our actions, or non-actions, is guilt. I agree that it helps us to accept responsibility for our actions. However, although it is quite obvious that guilt is a very effective tool for morality, I am still wondering if guilt is completely necessary. Can one be moral, or develop good moral character, without the influence of guilt? Thoughts, anyone?