grist for the mill vs luck

grist for the mill

noun
  • Something that is useful or that creates a favorable opportunity. 

luck

noun
  • Something that happens to someone by chance, a chance occurrence, especially a favourable one. 

  • The results of a random number generator. 

  • A superstitious feeling that brings fortune or success. 

  • Success. 

verb
  • To find something through good fortune; used with into, on, onto or upon. 

How often have the words grist for the mill and luck occurred in a corpus of books? (source: Google Ngram Viewer )