think before doing
think before (doing something)
To ruminate, reflect, or consider very carefully before undertaking some action. He's the type of person who wouldn't think before jumping on a plane to some foreign country on the promise of adventure. You really ought to think before taking on such a huge responsibility.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
think before doing something
to consider the consequences before doing something. You really ought to think before you take on a job like that. I finally learned to think carefully before accepting jobs like the one I just took on.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.