The achievement you earned does not need to be made smaller to keep other people comfortable.

Shrinking good news is such a reliable habit that it can pass for manners. You mention the thing while apologizing for mentioning it, or bury it inside qualifications until nobody could congratulate you if they wanted to. The discomfort being managed usually belongs to someone else, and modesty is not the same as disappearing.

Say one true sentence about something you did, with no hedge at either end. Let the pause afterward be theirs to fill rather than yours to rescue.