מדרש על תהילים 38:11

Three things cause to reduce the strength of man: fear, travel and sin. Fear, as it is written (Ps. 38, 11) My heart fluttereth, my strength faileth me; travel, as it is written (Ib. 102, 24) He hath shortened my days; Sin, as it is written (Ib, 31, 11) My strength faileth me because of mine iniquity.