Those whom success induces to relax their habits of care and thoughtfulness, and their willingness to encounter disagreeables, seldom long retain their good fortune at its height.
 John Stuart Mill, Considerations on Representative Government (1861). copy citation

Context

“If there is any thing certain in human affairs, it is that valuable acquisitions are only to be retained by the continuation of the same energies which gained them. Things left to take care of themselves inevitably decay. Those whom success induces to relax their habits of care and thoughtfulness, and their willingness to encounter disagreeables, seldom long retain their good fortune at its height. The mental attribute which seems exclusively dedicated to Progress, and is the culmination of the tendencies to it, is Originality, or Invention. Yet this is no less necessary for Permanence, since, in the inevitable changes of human affairs, new inconveniences and dangers continually grow up, which must be encountered by new resources and contrivances, in order to keep things going on even only as well as they did before.” source