A cat on hot bricks or cat on a hot tin roof: restless or skittish, unable to remain still.
Burn one’s boat or burn one’s brodge: do something that makes it impossible for you to change your plans and go back to the situation you were in before.
On slippery slope: in a situation that is likely to become more difficult or complicated.
The buck stops here: willing to take responsibility.
Learn the hard way: learn something by experience.
Freeze someone out: to shut out or exclude, as by cold or unfriendly treatment.
Fly on the wall: an unseen or unnoticed presence in a situation.
Blood run cold: to be very frightened.
Be at the end of your tether or be at the end of your rope: to be so tired, worried, or annoyed by something that you feel unable to deal with it any more, at the limit of your patience or endurance.
Get/take the bit between your teeth or take the bit in your teeth: to start doing something in a very keen way.
With one’s eyes wide open: totally aware of what is going on.
Last straw: the last of a series of annoyances or disappointments that leads one to a final loss of patience, temper, trust, or hope.
Have a clear conscience (about someone or something) or have a clean conscience (about someone or something): to be free of guilt about someone or something.
Lay one’s cards right or play one’s cards well: to work or negotiate correctly and skillfully.
Heart in your mouth: nervous or scared.
Send chills down/up somebody’s spine: to make someone feel very frightened.