jump the gun (?.)

• anticipate
• be predisposed
• burn to
• chafe
• foreglimpse
• forejudge
• forerun
• foresee
• forestall
• foretaste
• fret
• fuss
• get ahead of
• get excited
• go before
• go off half-cocked
• hardly wait
• hasten
• itch to
• judge beforehand
• preconceive
• preconclude
• predecide
• predetermine
• prejudge
• presume
• presuppose
• presurmise
• squirm
• stew
• sweat
• sweat and stew
• sweat it out
• wait impatiently
• win the start