Generally when you are just sucking for a period of time. It often refers to the academic ability of an individual. It is possible to earn ones way out of a slump, which is usually followed by a victory dance.
'Slumped' from October 2010 to February 2011 after a series of academic failures. With his return to glory being fueled by his story 'Piano Man'. A tale of a man whose life journey of not belonging is told through his music on stage - an instant classic.