When it comes to self-promotion, it seems like people take one of two polarized approaches. There are those who jump all-in and self-congratulate to the fullest ("Did you hear? I just won Employee of the Year! I mean it's not like I'm shocked, I did close some huge deals last month."), while at the other end of the spectrum are those who avoid all self-promotion and humbly go through life, taking all precautions to avoid being dubbed "that guy who self-congratulates to the fullest."
It's not hard to understand the lack of a happy medium. There is a fine line between bolstering your professional image, or that of your business, and coming across as self-absorbed and narcissistic -- hence the seemingly black-and-white nature of self-promotion.