Charles Darwin beginning the process of writing Origin of Species. Impressed by his own "industry" that went into research:
When I see the list of books of all kinds which I read and abstracted, including whole series of Journals and Transactions, I am surprised at my industry.
The items that lead to breakthroughs are seemingly random. 15 months into the process a random read enabled him to solidify his thoughts:
In October 1838, that is, fifteen months after I had begun my systematic enquiry, I happened to read for amusement Malthus on Population, and being well prepared to appreciate the struggle for existence which everywhere goes on from long-continued observation of the habits of animals and plants, it at once struck me that under these circumstances favourable variations would tend to be preserved, and unfavourable ones to be destroyed. The result of this would be the formation of new species. Here, then, I had at last got a theory by which to work.
After the age of 30 he stopped being interested or entertained by poetry / Shakespeare / plays / music.
I have also said that formerly pictures gave me considerable, and music very great delight. But now for many years I cannot endure to read a line of poetry: I have tried lately to read Shakespeare, and found it so intolerable dull that it nauseated me. I have also almost lost any taste for pictures or music...this curious and lamentable loss of the higher aesthetic tastes is all the odder, as books on history, biographies and travels and essays on all sorts of subjects interest me as much as ever they did.
Why does he think he was successful?
What is far more important, my love of natural science has been steady and ardent. This pure love has, however, been much aiided by the ambition to be esteemed by my feller naturalists.