The most important part of my “everyday carry” is not my pocket knife. It’s my slim and easy to tote copy of Seneca’s Moral Essays, Volume II. Why? Passages like this:

But it does no good to have got rid of the causes of individual sorrow; for one is sometimes seized by hatred of the whole human race. When you reflect how rare is simplicity, how unknown is innocence, and how good faith scarcely exists, except when it is profitable, and when you think of all the throng of successful crimes and of the gains and losses of lust, both equally hateful, and of ambition that, so far from restraining itself within its own bounds, now gets glory from baseness — when we remember these things, the mind is plunged into night, and as though the virtues, which it is now neither possible to expect nor profitable to possess, had been overthrown, there comes overwhelming gloom.

We ought, therefore, to bring ourselves to believe that all the vices of the crowd are, not hateful, but ridiculous, and to imitate Democritus rather than Heraclitus. For the latter, whenever he went forth into public, used to weep, the former to laugh; to the one all human doings seemed to be miseries, to the other follies. And so we ought to adopt a lighter view of things, and put up with them in an indulgent spirit; it is more human to laugh at life than to lament over it. Add, too, that he deserves better of the human race also who laughs at it than he who bemoans it; for the one allows it some measure of good hope, while the other foolishly weeps over things that he despairs of seeing corrected.

From De Tranquillitate Animi – On Tranquillity of Mind