I am grieved to hear that your friend Flaccus is dead

I am grieved to hear that your friend Flaccus is dead, but I would not have you sorrow more than is fitting. That you should not mourn at all I shall hardly dare to insist; and yet I know that it is the better way. But what man will ever be so blessed with that ideal steadfastness of soul, unless he has already risen far above the reach of Fortune? Even such a man will be stung by an event like this, but it will be only a sting. We, however, may be forgiven for bursting into tears, if only our tears have not flowed to excess, and if we have checked them by our own efforts. Let not the eyes be dry when we have lost a friend, nor let them overflow. We may weep, but we must not wail.

The position is precise. The complete absence of grief — the freedom from disordered pathē — is not the standard. Seneca explicitly refuses to insist on it and admits that even the sage would feel the sting. What the trained Stoic aims for is eupatheia, the well-ordered emotion: weeping, yes; wailing, no. The grief that overflows, that becomes performance, that does not eventually move toward acceptance, is the failure mode. We may weep, but we must not wail.

The conceptual frame Seneca is working in here is the same one Epictetus later puts in the Enchiridion 11 — that nothing we have was ever truly ours; everything is held in custody, returnable. Seneca was writing decades before the Enchiridion existed, so he does not cite Epictetus directly; but the underlying Stoic doctrine of grief-as-custody-loss is shared. The friendship was always borrowed. The loss is real. The pretense that it should never have ended is what makes the grief unbearable.

For my part, I do not agree with [Attalus]. To me, the thought of my dead friends is sweet and appealing. For I have had them as if I should one day lose them; I have lost them as if I have them still.

You have buried one whom you loved; look about for someone to love. It is better to replace your friend than to weep for him. […] A man ends his grief by the mere passing of time, even if he has not ended it of his own accord. […] I should prefer you to abandon grief, rather than have grief abandon you; and you should stop grieving as soon as possible, since, even if you wish to do so, it is impossible to keep it up for a long time.

The final move is the operational one: grief is allowed, even required, but not as a permanent state. Time will resolve it; reason can resolve it sooner. The work of the grieving party is to participate, with reason, in what time would do anyway — neither suppressing the grief nor staying inside it past its useful span.