Whenever you would attempt anything, first form an estimate both of your own powers, of the extent of the matter which you are undertaking, and of the means by which you are to accomplish it: for if you have to abandon your work when it is half done, the disappointment will sour your temper. In such cases, it makes a difference whether one is of an ardent or of a cold and unenterprising temperament: for failure will rouse a generous spirit to anger, and will move a sluggish and dull one to sorrow. Let our undertakings, therefore, be neither petty nor yet presumptuous and reckless: let our hopes not range far from home: let us attempt nothing which if we succeed will make us astonished at our success.