I don't consider myself a Federer fan even though I enjoy watching him play, but this is sad, you can feel he truly loves the game so much and would want to play forever, growing old if your passion in life is high level sport (it's different for artists) really s*cks and this is a good example of it.
Even though he is maybe done I admire a lot his willingness to still want to come back, against the time that is passing and against his body getting older and older, to still play like in the old days, his determination and dedication is still there, after more than 20 years of playing tournaments. He is inspiring.
In fact, even more than their games, the will power of the Big 3 is maybe what impresses me the most