One objection to Humean views about motivation, and to the 'Standard Model' of intention on which intentions are complexes of desire and belief, is that these views don't allow agents to choose their reasons for doing some action. In Reasons Without Rationalism, Kieran Setiya presents the Standard Model as unable to explain how "Our reasons are in some sense 'up to us' -- we decide why to do something, as well as what to do -- and we seem to recognize our reasons, as such" (39). Similarly, in Rationality in Action John Searle objects to desire-belief views of motivation, writing that "when one has several reasons for performing an action, one may act on only one of them; one may select which reason one acts on" (65).
I can see where these objections are coming from. On a traditional Humean picture, reason is the slave of the passions, and it doesn't have the ability to hold one desire back so that another can motivate action. Neither can it noninstrumentally create or strengthen a desire so as to make it and not another desire decisive in motivating action. Nevertheless, I think a traditional Humean approach on which all motivating reasons are desire-belief pairs and all practical reasoning is instrumental can explain reason-choosing. Let me show how this works.