Opinions, here.
There is a difference between bragging and letting people know when something good happens to you. Bragging is socially aggressive; it is attractive only to those who thrive on competitive relationships.
Bragging is the act of demanding social status and recognition of one's accomplishments or properties. It is explicitly a form of self-promotion.
Letting people know when something good happens to you means sharing your happiness (and perhaps even pride) with them. It means being happy and telling people why you're happy. It places them in a position of judgement over your accomplishment. It does not prejudge its value, or challenge them to recognize that value; it inherently risks rejection, and it is a conversation that occurs in the context of your relationship to that person.
The self-promotional message, no matter how well handled, is essentially a form of impersonal communication; the information one wishes to share needs to be shared with as broad an audience as possible.
I do not think that there are nearly as many people who are annoyed by good things happening to other people as there are people who are annoyed by bragging and self-promotion. Nor do I think that those who are not annoyed by bragging and self-promotion are necessarily genuinely happy for your success.
Thus I do not think that self-promotion will optimize your social relationships if their utility is considered to be their ability to support and nurture you as a human. I think that it would optimize your social relationships for the inclusion of self promoters and socially competitive peers, and the exclusion of those who prefer cooperative or individually unique, shared-intimacy-based relationships.