If something or someone is in fine fettle, they are in very good condition or health

If you lose track of something, you no longer know what is happening to something.

If you pick up/take up the ball and run with it, you take over something started by someone else, especially when they were not able to complete it.

A whale is a serious gambler, a high roller.

In AmE to give someone the hairy eyeball is to look at them askance.

If you poke your nose in or into something, it means you are interfering or too interested in someone else's business. 

If you throw in the sponge, you give in and admit defeat.

If your are energetic and vigorous, you are feeling your oats.

If something has gone for a ball of chalk, it has gone terribly wrong.

If you shake in your boots, you are terrified.
(Quake/cower in your boots are also used. You can also shake in your shoes.)