Stop worrying about how you sound when giving public presentations!
Confidence in public speaking comes from solid data and good technique. If you're stating opinion, rather than using data, then you have to qualify that to shield yourself.
So, if you're worried that you sound ridiculous, blame the data. If you're worried that your opinion is ridiculous, blame your experience.
After all, it's the reason's fault it sounds ridiculous, not yours. #trust
