can't wait vs look forward to

can't wait

verb
  • To eagerly anticipate; to find it hard to wait for a forthcoming pleasurable event. 

  • To need to be attended to right away. 

look forward to

verb
  • To anticipate, expect, or wait for, especially with a feeling of approval or pleasure. To be excited or eager to. 

How often have the words can't wait and look forward to occurred in a corpus of books? (source: Google Ngram Viewer )