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Phrase(s): Tomorrow is another day.
Prov. Things may improve tomorrow; tomorrow you will have a chance to solve the problems that are upsetting you today. (Often used to encourage someone to relax and wait until tomorrow to do or worry about something.) • Child: This math homework is horrible! I can’t do it! Mother: Put it away for tonight and go to bed. You’ll be able to think more clearly when you’ve had some sleep, and tomorrow is another day.
McGrawhill's American Idioms And Phrasal Verbs
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One may not accomplish everything today but will have another chance. For example, We've stuffed hundreds of envelopes and still aren't done, but tomorrow is another day. This comforting maxim was first put as Tomorrow is a new day about 1520, was widely repeated, and changed to its present form in the mid-1800s.
American Heritage Idioms