This may be my favorite quote in all the Platonic works, and the one I go back to when tempted by despair of philosophy.
" 'Then, Phaidon', he said, 'it would be a pitiable disease, when there is an argument true and sound, and such as can be understood, if through the pain of meeting so many which seem sometimes to be true and sometimes not, instead of blaming himself and his own clumsiness a man should in the end gladly throw the blame from himself upon the arguments, and for the rest of his life should continually hate and abuse them, and deprive himself of the truth and the knowledge of what is real.'
... 'First, then, let us be careful', he said, 'and let us not admit into our souls the belief that there really is no soundness or health in arguments. Much rather let us think that we are not sound ourselves, let us be men and take pains to become sound: you and the others to prepare you for all your coming life, I to prepare myself for death.'"
- Phaedo, from the WHD Rouse translation.