(if you) sing before breakfast, (you'll) cry before night

(if you) sing before breakfast, (you'll) cry before night

1. proverb If you are too joyous or optimistic at the start of the day, you run the risk of having a far fouler mood by the end of it. The grumpy old man, ever intolerant of others' happiness, scolded the girl humming to herself, saying, "If you sing before breakfast, you'll cry before night!" A: "I thought the day was going to turn out so well, but everything has gone wrong!" B: "Ah, well, sing before breakfast, cry before night."
2. proverb One should not celebrate one's achievements before one's business has actually begun. A: "This new product is going to launch our company back to the forefront of the industry!" B: "Maybe let's wait until it's actually on the market before patting ourselves on the back. If you sing before breakfast, you'll cry before night."
See also: before, cry, night, sing
Farlex Dictionary of Idioms.

sing before breakfast, you'll cry before night

 and sing before breakfast, you'll cry before supper
Prov. If you wake up feeling very happy, your mood will change before the end of the day. Jill: I woke up in such a good mood today. I don't even know why, but everything seems good. Jane: Sing before breakfast, you'll cry before night. Alan: Good morning, dear! Isn't it a wonderful day? I feel great. Jane: Sing before breakfast, you'll cry before supper.
See also: before, cry, night, sing
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • sing before breakfast, you'll cry before night
  • supper
  • (if you) sing before breakfast, (you'll) cry before supper
  • teach a man to fish
  • it takes a village
  • village
  • best-laid plans go astray, the
  • the best-laid plans
  • the best-laid plans go astray
  • the best-laid plans of mice and men