Modesty is considered a virtue. People respect and appreciate a becoming modesty in anyone.
But modesty and self-deprecation are different. Self-deprecation is usually something else in disguise, whether it’s whining and complaining or fishing for compliments. People usually see through it and get tired of the pretense and the implicit demand—for sympathy, praise, reassurance, or just attention.
Inviting others to celebrate and enjoy the news of your good fortune is also different from bragging. Perhaps it’s partly a matter of delivery and partly choosing your audience and your occasion. No one I know would be resentful or put me down if I announced that my son was graduating with honors. But I would expect only a few to enjoy hearing that he was graduating with the highest honors and at the top of his class.
Likewise, if the conversation is about health and weight, people will congratulate you if you report that you’ve lost 12 pounds doing yoga. But if they’re all moaning about their struggle, they don’t want to hear you say that you can eat half a chocolate cake and not gain an ounce.
Maybe we could put it in terms of giving and taking. Sharing good news is giving. When you answer a “how are you?” greeting with a hearty “I feel great!”, that’s giving. Lamenting and complaining, on the one hand, and demanding to be admired and applauded, on the other, are taking. Better save those for your closest chums and spare the rest.