Momentary impulses to boast cause me to feel shame. It's so strong that I can't say something good about myself in a job interview, not even that I'm confident about something. It's not that I don't want to - just that I tend to view boasting in others as suspect - so I expect that others would react the same way to me. If something is important for a particular reason, rather than talk about it, I'd prefer to let someone see the evidence.