Besides this, there are still other causes that tend to uproot from our minds services that sometimes have been very great. The first and most powerful of all is the fact that, busied as we are with ever new desires, we turn our eyes, not to what we possess but to what we seek to possess. To those who are intent upon something they wish to gain all that they have already gained seems worthless. It follows too, that, when the desire of new benefits has diminished the value of one that has already been received, the author of them also is less esteemed. We love someone, and look up to him, and avow that he laid the foundation of our present position so long as we are satisfied with what we have attained; then the desirability of other things assails our mind, and we rush toward those, as is the way of mortals, who, having great things, always desire greater. And everything that we were formerly inclined to call a benefit straightway slips from our memory, and we turn our eyes, not to the things that have set us above others, but to the things that the good fortune of those who outstrip us displays. But it is possible for no man to show envy and gratitude at the same time, for envy goes with complaint and unhappiness, gratitude with rejoicing.
In the second place, because each one of us is actually aware of only the particular moment of time that is passing, only now and then do men turn their thought back to the past; so it happens that the memory of our teachers and of their benefits to us vanishes because we have left boyhood wholly behind; so, too, it happens that the benefits conferred upon us in youth are lost because youth itself is never relived. No one regards what has been as something that has passed, but as something that has perished, and so the memory of those who are intent upon a future benefit is weak.