An eager Zen student arrives at a temple and says "I want to join the community and work to attain enlightenment. How long will it take me?"
"Ten years" replies the master.
"Well, how about if I really work and double my efforts?"
"Hey, just a moment. That's not fair! Why did you double it?"
"In your case," says the master, "I'm afraid it will be thirty years."
From "After the Ecstacy, the Laundry" by Jack Kornfield.