1. start planning something again
that plan didn't work so we need to go back to the drawing board
The literal use of a drawing board is to prepare a design, plan, or blueprint. Therefore, this expression refers to the need to revise or begin something again, typically as a result of a previous failure. Its use is very common in a professional context, where it is usually said after a setback. The need to go 'back to the drawing board' may arise as a result of a failure, but it often provides the opportunity to learn important lessons and then come back stronger, and more successful than before. For that reason, the term does not always mean a disaster or something entirely negative. A phrase with a similar meaning is 'back to square one.'