Be honest, how many certificates do you have? Count them all -- in your desk drawer, on the wall, in the ashes in the incinerator.
If you're American, its possible to live your entire life having received only one certificate -- your birth certificate. Only when you die is it considered a big enough event to give you another certificate.
Since I came to Japan, however, I have accumulated a drawer full of certificates: for karate, for Japanese language courses, for breathing, and the most recent one, for participating in orienteering.