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..."
Stay calm
Keep an idea in ones head to act on it later.
The idiom "keep your head in the clouds" means someone who is unrealistic or impractical in their thinking, often dreaming or imagining things that are not grounded in reality. It suggests that the person is not paying attention to practical matters and is more focused on daydreaming or fantasizing.
The head person.
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.
"Dive in head first" is to rush into a situation without thinking.
Keep bothering someone.
To turn completely around and head back in the direction you came from.
It means " keep calm, don't get worked up"
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.