forget it vs sure thing

forget it

verb
  • Don't let it bother you; put it out of your mind. 

  • I don't want to continue with this conversation (usually used in frustration or anger). 

  • It doesn't matter. 

  • A conventional reply to an expression of gratitude. 

  • Absolutely not; I forbid it or it is impossible. 

sure thing

noun
  • That which is certain. 

intj
  • An affirmative reply; yes; certainly. 

  • A polite reply to thank you. 

How often have the words forget it and sure thing occurred in a corpus of books? (source: Google Ngram Viewer )