Akademik

не все коту масленица
НЕ ВСЕ КОТУ МАСЛЕНИЦА (, БЫВАЕТ И ВЕЛИКИЙ ПОСТ)
[saying]
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life is not made up of pleasures alone - troubles and difficulties also occur (said when a time full of worries and cares comes to replace a period that is pleasant and carefree):
- - every day is not Sunday (a holiday);
- into each life a little rain must fall;
- [in limited contexts] all good things (must) come to an end.

Большой русско-английский фразеологический словарь. — М.: ACT-ПРЕСС КНИГА. . 2004.