One of the most important philosophers to read for your personal development is Aristotle. Also, read the book of Proverbs. It has hints for becoming charismatic, managing your money, flirting, being happy, and even going to heaven.
In his rhetorical manual, Aristotle observes this (just read the bold to get the main point):
But since rhetoric exists to affect the giving of decisions—the hearers decide between one political speaker and another, and a legal verdict is a decision—the orator must not only try to make the argument of his speech demonstrative and worthy of belief; he must also make his own character look right and put his hearers, who are to decide, into the right frame of mind. Particularly in political oratory, but [25] also in lawsuits, it adds much to an orator’s influence that his own character should look right and that he should be thought to entertain the right feelings towards his hearers; and also that his hearers themselves should be in just the right frame of mind. That the orator’s own character should look right is particularly important in political [30] speaking: that the audience should be in the right frame of mind, in lawsuits. When people are feeling friendly and placable, they think one sort of thing; when they are feeling angry or hostile, they think either something totally [1378a] different or the same thing with a different intensity: when they feel friendly to the man who comes before them for judgement, they regard him as having done little wrong, if any; when they feel hostile, they take the opposite view. Again, if they are eager for, and have good hopes of, a thing that will be pleasant if it happens, they think that it certainly will happen and be good for them: whereas if [5] they are indifferent or annoyed, they do not think so.W. Rhys Roberts, “RHETORICA,” in The Works of Aristotle, ed. W. D. Ross, trans. W. Rhys Roberts, E. S. Forster, and Ingram Bywater, vol. 11 (Oxford: The Clarendon Press, 1924).
The point Aristotle is making is about speech giving, but I think it is also a useful point for things like making friends and avoiding unnecessary conflict. Aristotle is noting the importance of maintaining and producing a certain frame of mind when you have social goals (in this case debating or convincing a crown during a speech).