appetite comes with eating

burn that bridge when one comes to it

To anticipate dealing with a problem or situation either by acting in a manner that alienates or cuts ties with others, or merely with the expectation of encountering trouble.

cross that bridge when one comes to it

To deal with a problem or situation only if and when it arises.

one's ship comes in

One makes or comes into possession of a significant amount of money.

take something as it comes

To accept and deal with something (an event, etc.) as it occurs, with a composed state of mind.

what's eating

What is wrong with...? What is the problem with... (somebody)? Inquired regarding somebody who seems upset, worried, angry, etc.

what's eating you

What is annoying or bothering you?

when push comes to shove

When the pressure is on; when the situation is critical or urgent; when the time has come for action, even if it is difficult.

worst comes to worst

If a possible worst-case scenario actually occurs.