CLVI
First of all, condemn the life thou art now leading: but when thou hast condemned it, do not despair of thyself--be not like them of mean spirit, who once they have yielded, abandon themselves entirely and as it were allow the torrent to sweep them away. No; learn what the wrestling masters do. Has the boy fallen? "Rise," they say, "wrestle again, till thy strength come to thee." Even thus should it be with thee. For know that there is nothing more tractable than the human soul. It needs but to will, and the thing is done; the soul is set upon the right path: as on the contrary it needs but to nod over the task, and all is lost. For ruin and recovery alike are from within.
http://classics.mit.edu/Epictetus/goldsay.2.2.html