Still, we think that weakness of will is a paradigm form of practical irrationality. So this goes to show that there is more to rationality than just reasoning. According to Raz's Irrationality Test: "if the exercise of a capacity can be non-derivatively irrational then the capacity is one of our rational powers." (p.4) So understood, our rational powers include not only good reasoning, but also measured emotions, decisiveness, strength of will, etc.
This also fits with his answer in 'The Myth of Instrumental Rationality' to the question "what are one's rational capacities?" (p.25)
They are those capacities that are involved in discerning which features in the world merit a response, and how to respond to them, including both intellectual and motivational capacities (such as deliberative capacities, ability to come to a conclusion and to stick to it).
Seems hard to disagree with.