His writing was highly influenced by his own life, which was every bit as extravagant as Gatsby's. Like Gatsby he fell in love with a woman whom he had to 'prove' himself to (both monetarily and otherwise). He lived a fairly wealthy lifestyle his entire life. He was involved briefly in World War 1. What influenced him was all of the changes that he lived through and saw, and the extreme changes that money had on people (good and bad).