Definitions:

1. Informal slang phrase meaning to gather courage, toughen up, or face a challenge without fear or complaint. VERB
   • If you're going to compete you need to sack up and play hard.
2. Means to man up, get brave, or take responsibility, especially in the face of fear, pressure, or adversity. VERB
   • If you want to succeed, you must be willing to sack up and do the hard work.
3. Used to tell someone to stop being afraid and to have the courage to do something difficult, challenging, or scary. VERB
   • It's time to stop making excuses and sack up about your mistakes.

Synonyms:

• face the music
• get it together
• Man up
• step up
• toughen up