hold back

verb3

1. •
   To act with reserve; to contain one's full measure or power.

   • Don't hold back. Hit it as hard as you can.
2. •
   To contain; stop.

   • The dam can't hold back that much water.
   • I was swallowing hard to hold back the tears.
3. •
   To delay the progress of, especially in school.

   • He's a year older than his classmates, because he was held back in second grade.