Play it by ear

Play it by ear

Meaning:

Decide what to do or say according to a situation as it develops.

If you play it by ear, you act by responding a situation as it happens, rather than following a plan you made in advance.

Example:

We can't plan for today's interview. Let's just go and play it by ear.

They can't predict what will happen in tomorrow's game, so they decided to play it by ear.