The friendship of the bad is ...

The friendship of the bad is like the shade of some precipitous bank with crumbling sides, which, falling, buries him who is beneath.
 J. K. Bharavi

Quotes from the same author

Be patient, if thou wouldst thy ends accomplish; for like patience is there no appliance effective of success, producing certainly abundant fruit of actions, never damped by failure, conquering all impediments.
 J. K. Bharavi