“A losing battle”

“Get cold feet”

To become nervous and change your mind.

“Beat a dead horse”

To waste time on something already decided.

“Better late than never”

Doing something late is better than not doing it at all.

“A blessing in disguise”

Something that seems bad but turns out good.

“Wrap one's head around something”

To understand something complicated.

“Catch someone red-handed”

To catch someone in the act of doing something wrong.

“Every cloud has a silver lining”

There is something good in every bad situation.

“Time flies”

Time passes very quickly.