An idiom is something that does not mean what the phrase says literally, so yes. You can't actually laugh your head off.
This is not an idiom - it means exactly what it says. You should stay fit and healthy.
To turn completely around and head back in the direction you came from.
If used as an idiom, it usually means that you are confused about something. The image is of you scratching your head to try to think better.
"Keep your hair on" could refer to the Old West, when Indians might scalp you if you were not watchful. I've never heard it said as "keep your hair on" though.I suppose the idiom 'keep your hair on' means that if when a person is stressed the likelyhood that you could lose your hair or even pull it out hence keep it on and keep yourself calmThis may be a mixed idiom - more common is "keep your hat on" which is also means keep calm and don't "blow your top"."Keep your hair on" is advice telling someone to keep calm and not to over-react or get angry.
If your head is "in the clouds," you're a dreamer.
Keep an idea in ones head to act on it later.
It means to remain calm and rational in the middle of a chaotic or confusing situation. The poem "If" by Rudyard Kipling begins: "If you can keep your head when all about you/ are losing theirs and blaming it on you..."
The head person.
To have a cool head is to have "the ability to stay calm and think clearly in a difficult situation." It is an idiom and does not mean to literally have a cold head, but to be able to make level-headed decisions and remain calm and collected.
An idiom is something that does not mean what the phrase says literally, so yes. You can't actually laugh your head off.
This is not an idiom - it means exactly what it says. You should stay fit and healthy.
To keep struggling and not give up.
it means that
A level of craziness comparable to that of a bedbug.
"Dive in head first" is to rush into a situation without thinking.
Keep bothering someone.