To lose your marbles is to go mad. This is an idiom used in informal contexts.

• Rahul was earning a six figure salary so his decision to quit his job puzzled his parents. They thought that he had lost his marbles.

• Have you lost your marbles? Why don’t you lock the doors before you leave?

• Uncle Gupta has lost his marbles but that is hardly surprising. He is ninety-eight.

• Uma must have lost her marbles. She has put her five-year old daughter on a diet.

• The man said that he would lose his marbles if he spent another day with his wife.

If somebody is mentally sound, then you can say that they have all their marbles.

• My grandmother is over 90 years old, but she still has her marbles.

Lose one’s shirt

To lose one’s shirt is to lose all that one possesses – even one’s shirt.

• He tried his luck in stock market without understanding anything about trading and almost lost his shirt. (= He lost a lot of money.)

• He almost lost his shirt when the film he produced failed at the box office.

• If you don’t invest more wisely, you will lose your shirt.

• “Could you lend me $200?” “I’m afraid not. I just lost my shirt in gambling.”