Letters from a Stoic 10 : 2

When persons are in mourning, or fearful about something, we are accustomed to watch them that we may prevent them from making a wrong use of their loneliness. No thoughtless person ought to be left alone; in such cases he only plans folly, and heaps up future dangers for himself or for others; he brings into play his base desires; the mind displays what fear or shame used to repress; it whets his boldness, stirs his passions, and goads his anger. And finally, the only benefit that solitude confers, – the habit of trusting no man, and of fearing no witnesses, – is lost to the fool; for he betrays himself. Mark therefore what my hopes are for you, – nay, rather, what I am promising myself, inasmuch as hope is merely the title of an uncertain blessing: I do not know any person with whom I should prefer you to associate rather than yourself.