This raises a number of issues. Perhaps the categories you are identifying (most wanted, where you want to be, most useful, most needed, more rational) need to be subordinated to the concept what is good, irrespective of who wants what. So if you are choosing between two partners (to take your example) you might think first and foremost about whether the relatioship would be good (contribute to each other's flourishing, for example) for one or both of you and, once you have determined that, it will follow naturally (presumably) that you will want that which is mutually satisfying and fulfilling. Without identifying the context of a decision in terms of goods, just being needed by a person or thing would not itself be a good reasons for you to pursue or want that person or thing. I think the same is likely true in terms of wants. Merely wanting X (without any other information) may not be a sufficient reason to pursue X or to think it good for you to pursue X. If, however, you secure some concept of...

Good question(s). A range of philosophers have sought to argue that one should be moral out of self-interest. Some philosophers who argue that morality must lead to fulfillment (the virtuous should be happy) combine their ethics with a moral argument for God. Kant thought that for morality to make sense we need to have a kind of moral faith in God as an ideal judge who will insure that the good are rewarded, and the vicious are not. Still other philosophers will question the intelligibility of your question: asking why one should be moral may be likened to asking you should do what you should do. Questions like 'why is the sky blue' make sense, whereas 'why is blue, blue?' do not.