Full Idea
It is past failures (of training, discipline, reflection…), rather than a specific mental event, a choice or a decision, which in Aristotle accounts for akratic action.
Gist of Idea
Akrasia is explained by past mental failures, not by a specific choice
Source
report of Aristotle (Nicomachean Ethics [c.334 BCE], 1148a10) by Michael Frede - A Free Will 2
Book Reference
Frede,Michael: 'A Free Will' [Univ of California 2011], p.24
A Reaction
This is to demonstrate that Aristotle has no concept of a 'will' which arbitrates over difficult choices. What we call 'willing' he applies only to choices which are rational.