These antagonists, he [Diogenes the Cynic] remarked, appear formidable and irresistible to men rendered cowardly by their vices: but, whoever shall despise their power, and approach them boldly, such a combatant will discover them in experiment to be destitute of resolution, and unable to master their intrepid and vigorous opponents: like dogs exactly in this respect, which closely pursue the fugitive, and bite and tear, if they overtake him; but are terrified by one, who faces them with spirit, and retire from his approach; till at length they become so familiar and fond as to fawn upon him. The generality of mankind, alarmed by these adversaries, and always flying from their presence, so as never to confront them with their eyes, invite and stimulate their assaults.
It fares with men in this case, as with a pugilist; if he anticipate his antagonist, he is able to continue the combat, throws him down, and thus acquires a superiority in the conflict: but, if he recede through fear, he exposes himself immediately to the fiercest blows. Thus, Toils and Hardships exert no considerable power against one, who receives them with a contemptuous indifference, and resolutely closes with them; but assume a semblance of greater magnitude and more terrific aspect to every adversary, who retreats, and declines the contest.
You may descry an illustration of these sentiments in fire: if you trample upon it with violence and resolution, it is extinguished; but you will be severely scorched by assailing it with slackness and trepidation. Thus children, in their sportive recreations, will sometimes quench a flame even with their tongue. Antagonists of this intrepid character much resemble those athletic combatants, who employ all their strength, and watch every advantage, in the battle; striking, and throttling, and tearing, and sometimes eventually murdering, each other. (Dio Chrysostom, Diogenes, or Concerning Virtue)
Compare this to the metaphor of grasping a snake in this excerpt from Bion of Borysthenes.