On Grief by Baruch Spinoza — Read

Grief shall be the last of which we shall speak in our treatment of the passions, and with it we will conclude. Now grief is a certain kind of sorrow arising from the contemplation of some good which we have lost, and [lost] in such a way that there is no hope of recovering the same. It makes its imperfection so manifest that as soon as we only examine it we think it bad. For we have already shown above that it is bad to bind and link ourselves to things which may easily, or at some time, fail us, and which we cannot have when we want them. And since it is a certain kind of sorrow, we have to shun it, as we have already remarked above, when we were treating of sorrow.

I think, now, that I have already shown and proved sufficiently that it is only True Belief or Reason that leads us to the knowledge of good and evil. And so when we come to prove that Knowledge is the first and principal cause of all these passions, it will be clearly manifest that if we use our understanding and Reason aright, it should be impossible for us ever to fall a prey to one of these passions which we ought to reject. I say our Understanding, because I do not think that Reason alone is competent to free us from all these: as we shall afterwards show in its proper place.