My thoughts are very rough on this issue; as normativity/metaethics I find very very hard.
Lets ask a question about motivation; lets phrase it in a question such as “Why did Priam try to defend the Pergamum palace when the Greek alliance infiltrated?”
Lets say that the actual answer is up for grabs; but what I want to address is what kind of answer should we give?
We can talk about the beliefs, and desires of the agent, Priam; Priam is a proud man, proud of his kingdom of Troy, he believes it is something worth fighting for, even if it is inevitable he will lose. If he were not to fight, he would disrespect the nation he so loves and rules. We may call this an internalist type of reasons.
Now, there are strange cases where which we act so as not within our belief or desire-set. This sounds prima facie dubious; but let us consider it in terms of this; reasons for action where our own beliefs and desires are appealed to. There is an interesting case in Shafter-Landau about this. It is an interesting, yet difficult (namely, the literature is difficult) issue of how we go about answering the issues of what appeals we make as regards motivation.