Soldier On Meaning

Example :   He soldiered on through the night, working hard and not sleeping.  First boy:What do I do? I was playing in the house when I wasn't supposed to, knocked my mother's vase over and it broke. She thinks it just fell. How do I tell her?Second boy: It was a cheap vase; telling her will only make things bad for you. She doesn't need to know. Keep your mouth shut, soldier on and take it to your grave.