In Well temperaments, each of the 12 major and 12 minor keys was thought to have its own emotional quality. This is primarily due to the varying sizes of the major thirds in the Well temperaments, which dominated European music during the 17th, 18th and 19th centuries. The descriptions below are arranged according to the circle of fifths. You can see that the descriptions change from more peaceful around C major / A minor to more struggling/distressed around F# major / D# minor.

This is pretty interesting...

http://www.rollingball.com/A01c.htm