free rein vs self-control

free rein

noun
  • The absence of constraints; freedom to make decisions. 

  • Loose rein(s), as of a horse. 

self-control

noun
  • The ability to control one's desires and impulses; willpower. 

verb
  • To control oneself or itself. 

How often have the words free rein and self-control occurred in a corpus of books? (source: Google Ngram Viewer )