Не реви раньше смерти

Do not worry about a problem ahead of time

Cf: Call not a surgeon before you are wounded (Am.). Don't bid the devil good morning until you have met him (Am.). Don't climb the hill before you get to it (Br.). Don't climb the hill until you get to it (Am.). Don't cross the bridge before you get (till you come) to it (Am., Br.). Don't cross your rivers before you get to them (Am.). Don't cry before you are hurt (Br.). Don't cry till you are hurt (Am.). Enjoy the present moment and don't grieve for tomorrow (Am.). Never cross the stream before you come to it (Am.). Never howl till you are bit (Br.). Never howl till you are hit (Am.). Never meet trouble halfway (Am., Br.). Sufficient for (to, unto) the day /is the devil thereof/ (Am., Br.). Tomorrow can look after (can take care of) itself (Br.)