An essay of Isaac Asimov is published in MIT technology review titled “How do people get new ideas?“.
A remarkable idea of requirements for creativity is well expressed by the following paragraph:
“Probably more inhibiting than anything else is a feeling of responsibility. The great ideas of the ages have come from people who weren’t paid to have great ideas, but were paid to be teachers or patent clerks or petty officials, or were not paid at all. The great ideas came as side issues.”