Men are in general abundantly attentive to their own interest; if, therefore, you wish them to serve you with diligence, you must make it their interest to do so:

Hoc tibi sit argumentum, semper in promptu situm,
Ne quid expectes arnicos facere, quod per te queas. Be this your rule through life, never leave to others to perform any business for you, which you can do yourself: consonant to this we say, help yourself and your friends will love you