Michelangelo was not lazy but in his whole life—a long one—he finished only about twelve or fourteen statues. Why?
For one thing, he lost many years in the mountains of Carrara and Pietrasanta, quarrying the marble for his projects.
Pietrasanta (see this webpage)
The city of Carrara and its white marble quarries (Wikimedia commons photo, released into the public domain by its author, Arpingstone)
That was very hard and dangerous work which had nothing to do with aesthetics. He had to build a road out of the quarry of Pietrasanta to transport his blocks on oxcarts. Once he was nearly crushed when the chain holding a block broke. At night he had nothing to do but brood.
Here is a letter he sent from the Pietrasanta quarry to his helper Pietro Urbano in Florence.
April 20, 1519
Pietro: Things have gone very badly. On Saturday morning I began to raise a column as carefully as I could, forgetting no detail whatsoever. After it had been raised a hundred feet a link in the chain that held it snapped and it fell down into the river and broke into a hundred pieces. It was Donato who ordered that chain from his friend Lazzero the smith, and if it had been as strong as it should have, it could have held four columns that size. It looked fine from the outside—there was no reason to doubt it. After it broke we could see that it had been a fraud, since the inside wasn’t solid and was no thicker than the handle of a knife—and we wondered how it could have lasted so long. All of us who were working near it put our lives in danger and that beautiful stone was ruined….The iron was raw and of very poor quality and it was chosen by Donato together with his friend to be worked on the anvil. So you see how he filled my order and what patience I have to have. I won’t be home for this year’s fair but will stay here and, God willing, I will begin to work.
To see what Pietrasanta is like today and how marble is quarried, go to this very interesting webpage made by Professor Levey. Michelangelo wouldn’t believe his eyes.