to act boldly

• 不敢放胆。

  I don't have the courage.

• 放胆去做，不必害怕。

  Go ahead; don't be scared!

• 你尽管放胆试验，大家支持你。

  Just go ahead and try, we're right behind you!

• 他迟疑了一会儿，才放胆走进屋里。

  He hesitated for a moment before boldly walking into the room.