I recommend Kieran Setiya’s article “Is Philosophy Self-Help?” in The Point. Setiya has written serious philosophy that I have found helpful psychologically, and he has looked at the self-help business, starting with Samuel Smiles’ 1859 bestseller, Self-Help: With Illustrations of Character and Conduct.

Based partly on his article, I would emphasize these differences:

1. Self-help tries to meet the desires of the reader–usually but not invariably for happiness. In contrast, philosophy asks what the reader should desire. Personal happiness is one possible answer, but that is debatable in philosophy.
2. Self-help tries to serve the reader, addressing that person’s specific needs, values, and tastes. Philosophy asks whether human beings in general should pursue certain values. Some philosophers have given pluralist responses, emphasizing that individuals or cultures may or should hold different values. But such pluralism is, again, controversial in philosophy and would require a defense. As Setiya notes, “For Aristotle, the nature you should perfect is not your individual potential, but an objective human nature whose ideal expression lies in theoretical contemplation of the cosmos.”
3. Self-help influences individuals’ thoughts and choices. For some philosophers (e.g., Emerson) one’s self is the best topic, but for others, it’s essential to think about society and institutions, and possibly even to sacrifice oneself for them.

I’m in a reading group on Plato’s Republic, and all three differences between self-help and philosophy are already evident in the very first pages. Cephalus is presented as an old man who is happy. He has taken advice from Pindar and Simonides, whom he treats as self-help gurus. He has learned from them that he’s better off now that his appetites for sex and other desires have diminished. He derives serenity from reflecting on his own virtue.

Socrates is a threat to Cephalus’ happiness (and I am open to the possibility that Plato sees him as a menace). Socrates will not take Cephalus’ subjective beliefs for granted; he challenges the definition of justice that Cephalus has found in Simonides. He thereby demonstrates that Cephalus has drawn serenity from an unfounded belief in his own rightness.

Further, we know that Cephalus’ sons Polemarchus and Lysias (who are present in the dialogue) will later be selected to be two of the first ten victims of the Thirty Tyrants– Lysias narrowly escaping; Polemarchus suffering death. They will be singled out because, like Cephalus, they are wealthy resident aliens, not citizens. So we can see that Cephalus’ happiness is contingent on the accident that the city has chosen to treat him well. He should be thinking about how to secure justice for the community.

On the other hand, one might think that Cephalus is lucky not to get a full dose of Socrates. He leaves just before Socrates begins to critically analyze his beliefs, heading off to watch a civic/religious festival instead. I can read the portrait of Cephalus as elegiac: he fortunately lived a happy life to its conclusion before his happiness could be wrecked by either philosophy or politics.

See also: Pindar on hope; Cuttings version 2.0: a book about happiness; analytical moral philosophy as a way of life; Kieran Setiya on midlife: reviving philosophy as a way of life; etc.