1) ConfidenceHow do certain people feel so comfortable about themselves in front of others? Some people act silly or even stupidly yet they are so unconcerned. How do they do that?
and/or
2) Not worrying about what others think
#2 may depends on context - some people find it easier to act differently when they're with or around people that aren't in their usual social circles.
#1 is something that for some comes with time.