nerve up

verb3

1. •
   To get courage or strength.

   • I was still trying to nerve up to tell my dad I wasn’t going to Mass on Sunday anymore. — 1992
2. •
   Synonym of nerve (“to give courage or strength; to supply energy or vigour”).

   • Their influence goes far to nerve up the men to a constant fighting pitch, and no officer is tolerated away from his command unless sick or wounded. — 1863
3. •
   To make anxious.

   • was that why you hit him with the hammer because you were nerved up? — 1899