Humility makes you better at your job, but in many places it will prevent you from developing that job into a career.

Humility is what makes us recognize the weaknesses in our skill and knowledge, and what makes us seek feedback from others to hone that skill. I'm convinced that not being self-satisfied is key to becoming a master craftsmen. But, if you don't advertise your own skill, people will think less of you than you really are, and you won't get the jobs that you really want.