Long have a thought that there is a instinctual tie with mothers and breastfeeding. I had low supply with both of my sons. Intellectually, I knew that I was doing everything in my power to breastfeed them, but I'm a mammal, and mammals nurse their babies, so supplementing was a giant disappointment for me even though it was necessary. I believe that the mothering instinct (or hormones, or the way we have evolved - whatever combination is involved) to do things the way "nature intended," even when we realize that we're already doing our best, is so strong that mothers can feel a lot of disappointment/guilt over not doing whatever they consider to be "ideal."