What is the meaning of everything is same but everything is different ?
This is taken keeping "On the face of it" in mind. Here, they intend to tell that everything seems the same to everybody but in true sense, it is different. It is all based on the mindset of the individual viewing it. Seeing the same thing, with different perspective, changes that thing and its value. If we look into Mr. Lamb's and Derry's lives, we see that Mr. Lamb chose to view his disability in a positive manner and he made sure his disability did not get into the way of his joy whereas Derry saw his disability as a bane and saw it as a negativity of his life which inturn affected his joy.
Hope this helps.