be puffed up with pride

To be acting in a conceited or arrogant manner. The interviewer won't like you if you're all puffed up with pride when you meet with her. Self-confidence is essential, sure, but you have to learn not to be all puffed up with pride when things are going well. Thankfully, Bill isn't puffed up with pride now—he's still the same humble guy he's always been, just with a PhD.

be puffed up with ˈpride, etc.

be too full of pride, etc: He felt grown-up, puffed up with self-importance.