Hold Something Back

to restrain or control something, such as an emotion or a reaction, in order to prevent it from being expressed or revealed

I tried to hold back my tears when I heard the sad news.

She held back her laughter when she saw the silly joke.

to reserve or keep something, such as information or resources, for a later time or for a specific purpose

The company is holding back some of its best products for the holiday season.

I'm holding back some money for a rainy day.