First, give your writing a confidence edit by eliminating “throat-clearing” language like “I think” and simply say the thing you mean. That’s easy enough, but definitely also ruthlessly eliminate cutesy, meant-to-be-self-deprecating-so-you-feel-like-you’ve-preempted-any-reader-doubt-about-your-deservedness-and-made-it-safe-for-yourself-to-admit-a-thing language, too, like “Somehow, I did XYZ.” Somehow you did? Because we both know that the “somehow” means that you busted your ass and worked hard and got that thing done. Is it a fact? Did you do that thing? Then admit it and move on.
Hedging your credentials not only makes you look like you are not confident, but, it also casts a subtle message to the person on the receiving end of your statement that one some level, you don’t trust them to believe you, or worse of all, it creates the seed of thought that maybe you don’t know if you deserve your victories and credentials, either.
And, it’s a fair feeling. And, a feeling likely to worsen the more intimidating a room or audience feels, but fight it. Fight it because you deserve your credentials, fight it because your accomplishments help you establish yourself as someone to whom your reader should listen, and fight it because, deep down, I think we all know that someone who felt well-represented, and didn’t feel intimidated wouldn’t even flinch to share the same credential.