keep something to yourself

She decided to keep her plans to herself until the last moment.

她決定將她的計劃保密到最後一刻。

I know you want to share the news, but it's better to keep it to yourself.

我知道你想分享這個消息，但最好還是保密。

This secret is a promise between my family and me; I will keep it to myself.

這個秘密是我家人和我之間的承諾；我會保密。