
“If people knew how hard I had to work to gain my mastery, it would not seem so wonderful at all.”
Found attributed to Michelangelo in non-specialist publications as early as 1929 https://books.google.com/books?id=-0YhAQAAMAAJ&dq=If+people+knew+how+hard+I+had+to+work+to+gain+my+mastery%2C+it+would+not+seem+so+wonderful+at+all.&focus=searchwithinvolume&q=michelangelo, but no source is known. Not found in any known biography of Michelangelo.
Disputed