てはいられない

てはいられない says you can't afford to go on doing something, or to stay as you are, because the situation calls for action. It goes on the て-form of the verb, followed by は and いられない, the negative potential of いる: "can't stay doing".

The verb is often a feeling or a state you would like to stay in but shouldn't.

てはいられない or ずにはいられない

The two sound alike and point in opposite directions. てはいられない is "can't afford to keep doing it", so you stop. ずにはいられない is "can't help doing it", so you do it.

Usage notes

These go beyond the standard form.

ちゃいられない

In casual speech ては becomes ちゃ, and では becomes じゃ.

ている場合じゃない

ているばあい場合じゃない is close in meaning: "this is no time to be doing it". It judges the moment, where てはいられない reports what you yourself can't go on doing.