They have become the slaves of habits whose power they are impotent to resist.

Hence Locke has said that to create and maintain that vigour of mind which is able to contest the empire of habit, may be regarded as one of the chief ends of moral discipline.
Though much of the education of character by example is spontaneous and unconscious, the young need not necessarily be the passive followers or imitators of those about them.

Their own conduct, far more than the conduct of their companions, tends to fix the purpose and form the principles of their life.

Each possesses in himself a power of will and of free activity, which, if courageously exercised, will enable him to make his own individual selection of friends and associates.

It is only through weakness of purpose that young people, as well as old, become the slaves of their inclinations, or give themselves up to a servile imitation of others.
It is a common saying that men are known by the company they keep.