Full of yourself
Definition 1 of 1
Pro Tip 1/3Colloquial Use
The phrase is informal and often used in casual conversation, not in formal situations. 
He's started talking like he's the boss—so full of himself lately.
Pro Tip 2/3Negative Tone
'Full of yourself' carries a negative connotation, suggesting someone has an exaggerated sense of self. 
Ever since she won the award, she walks around full of herself.
Pro Tip 3/3Common Contexts
Used when someone is bragging or showing off, it's a way to criticize their behavior. 
You're acting too full of yourself; no one appreciates a show-off.