Bernhard Riemann: Turning points in the conception of mathematics 

The following paragraphs from the book tell a lot about Riemann. 

The degeneration of mathematics began with the ideas of Riemann, Dedekind, and Cantor, which progressively repressed the reliable genius of Euler, Lagrange, and Gauss. (C. L. Siegel, 1959) (Preface)

In 1857, after he had completed the two function-theoretic papers that engaged him completely, periods of depression set in. Dedekind speaks of spiritual fatigue and an utterly dark mood. (P 27)

His solitary life and, in addition, his physical suffering have made him extremely hypochondriac and mistrustful of other people and of himself, although he seems outwardly to be quite friendly. (P 28)