Wiktionary
comfortable in one's own skin
a. (context idiomatic English) relaxed and confident in one's manner of presenting oneself and interacting with others; conveying the impression that one has a clear, satisfying understanding of one's own abilities and situation. alt. (context idiomatic English) relaxed and confident in one's manner of presenting oneself and interacting with others; conveying the impression that one has a clear, satisfying understanding of one's own abilities and situation.