Thinking about the larger context:
It possible that the "calm" within Epicureanism is refering to the feeling which arises when one thinks about "when death is, I will not be" and the "gods do not punish" (they are not the cause of thunder and lightening and they are not involved with humans).
So it is not a "mind-over-matter" like in Hinduism or Buddhism, but rather reasoning through those two things (death and the nature of the gods).
Is there any other practices in Epicureanism besides these two, that would lead to a feeling of "calm"?