Braggers are the ones who are constantly desperate for the spotlight. The trumpets blow loud and continuously when something goes right for them. This need for constant praise, validation, etc stems from their lack of self-esteem and insecurities.
Your exciting news will always put them in a state of competition, instead of cheering you on. Braggers are also the sort who habitually self-deprecate just so that you can insist how awesome they are. It is infuriating and unhealthy to serve as a constant fuel of self-esteem for others, and you must avoid doing it.