The phrase "steel oneself" means to prepare oneself mentally or emotionally for a difficult task or situation. Some synonyms for this phrase include toughen up, fortify, brace oneself, gird oneself, gear up, and summon one's courage. These synonyms all convey the sense of preparing oneself for a challenge ahead, often involving a degree of courage and resilience. Other related phrases include psych oneself up, steel one's nerves, and ready oneself. No matter which phrase is used, the essence remains the same - to mentally prepare oneself for a challenge and face it head-on with determination and resolve.