Doesnt sound like an issue of hard work to me…sounds like you choke during the actual game…figure out what makes you comfortable in practice but uncomfortable in games. Is it the other players? fans? pressure? are you easily intimidated? Try to picture someone like Kobe or another big time pressure guy like Derek Jeter in your head and try to emulate their demeanor.
Sounds corny but it works. quick tidbit: I had some legal trouble a couple of years back (DUI etc etc) and one thing my lawyer told me was to not react to ANYTHING that was said because the jury would be watching me…who did I picture in my head to keep me even keeled? Joe Torre(yes I am a yankee fan incase you are wondering) The bailiff at one point asked my friends who were there to testify on my behalf how old I was becasue he couldn’t get a read on any of my emotions. long story short, not guilty.
It’s mental bro…get tough in the head and your abilities will take over.