Communicating (with a Handicap)

I was helping out in my parents' bakery the other day when a customer came in and pointed to a certain type of bread role and raised three fingers with the other hand. I then asked "Three pieces of this one?"
But then I realized that I would not get an answer... this particular customer was deaf-mute. I suddenly felt so guilty not being able to grasp her handicap, even worse: I would continue to talk to her even though I was fully aware of it by now... that just shows me how stupid normal  people actually can be, not being able to adapt to individual needs and even being overstrained with the situation.
I just think that this could teach all of us how lucky we are and that we should appreciate the simple things in life.

What's actually worse is when people without such a handicap are just not able to communicate with each other... be it due to a lack of interest or just the lack of social skills. This might be the cause for most of our problems concerning our extended family, our circle of friends and our coworkers as well, and maybe even  greater society.
Maybe I'm not even making sense...