Chrysippus, Fragments from the Passions 2

That is why it is not off the mark to say, as some people do, that a passion of the soul is an unnatural motion, as is the case with fear and desire and things like that; for all such motions and conditions are disobedient to reason and reject it. 

And so we say that such people are irrationally moved, not as though they make a bad calculation, which would be the sense opposite to "reasonably", but rather in the sense of a rejection of reason. . . . 

That is what such conditions are like, uncontrolled, as though they were not masters of themselves but were carried away in the way that those who run strenuously are swept away and cannot control their motion. 

But those who move according to reason, as though it were their leader, and steer their course by it wherever it might lead, these people are in control of this sort of motion and the impulses that go with it.