From "The Inner Citadel" by Pierre Hadot

     "Stoicism is often regarded as a philosophy of certainty and intellectual self-confidence. In fact, however, it was only to the sage - that is, to an extremely rare being who represented more an inaccessible ideal than a concrete reality - that Stoics attributed infallibility and perfect soundness of judgment. Most people, including philosophers - who, in their own view, are precisely not sages - must painfully orient themselves within the uncertainty of everyday life, making choices which seem to be justified reasonably - in other words, probabilistically."

     "Action thus risks introducing worry and care into the Stoic's life, to the same extent to which he does good, and where he intends to do good. By means of a remarkable reversal, however, it is precisely by becoming aware of the transcendent value of doing good that the Stoic can regain peace of mind and serenity, which will enable him to act effectively. There is nothing surprising about this, for it is precisely within the moral good - that is to say, the intention of doing good - that the good is situated for the Stoics.
     For the Stoics, intentions bear within themselves a value which infinitely transcends all the objects and 'matters' to which they are applied, for these objects and matters are in themselves indifferent, and only assume a value to the extent that they provide an opportunity for intentions to be applied and become concrete."

     "In Marcus Aurelius, but also in Epictetus and in Seneca, the vocabulary of the discipline of action includes a technical term meaning 'to act 'with a reserve clause' ' (Greek hypexairesis; Latin exceptio), which implies a transcendence of intention with regard to its objects. The idea of a 'reserve clause' reminds us that, for the Stoics, act and intention are fused into an inner discourse which enunciates, as it were, the plans of the agent. According to Seneca, the sage undertakes everything 'with a reserve clause,' insofar as he says to himself"
'I want to do thus and so, as long as nothing happens which may present an obstacle to my action.'
'I will sail across the ocean, if nothing prevents me.'
     Putting matters this way may seem banal and useless; from the Stoic point of view, however, it is full of meaning. In the first place, it reveals to us the seriousness of Stoic 'intention.' To be sure, Seneca's formula could be reduced to the following: 'I want to do x, if I can'; and it would be easy to joke about such a 'good intention' which quickly gives up its goal at the first difficulty that arises. In fact, however, the contrary is true. Stoic intentions are not 'good intentions' but 'intentions that are good' - in other words, firm, determined, and resolved to overcome all obstacles. It is precisely because the Stoic refuses to give up easily on his decision that he formulates a reserve clause, in quasi-judiciary terms."

      "The 'reserve clause' means that this firm decision and intention always remain integral, even if an obstacle should arise which prevents their realization. Such an obstacle is part of what the sage has foreseen, and it does not prevent him from willing what he wants to do. In the words of Seneca:
'Everything succeeds for him, and nothing unexpected happens to him, for he foresees that something may intervene which prevents him from that which he had planned to carry out.'"