assertive vs comfortable in one's own skin

assertive

adj
  • Boldly self-assured; confident without being aggressive. 

comfortable in one's own skin

adj
  • 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. 

How often have the words assertive and comfortable in one's own skin occurred in a corpus of books? (source: Google Ngram Viewer )