Get real folks. You don't deserve the tongue-lashing you just gave yourself. Missing that short forehand happens. You act like you've been practicing that shot for days.
Here's some coaching insight that may help you come to terms with your maddening mistakes: When training a player, the coach feeds hundreds, if not thousands of short balls, with the idea of getting past technique and into confidence. It's a simple formula: practice a shot enough times, and in a match, you expect to make it.
He makes a double fault and you don't think twice about it. You double fault and go crazy. Try this thinking for a change: his error is a gift, your makes it even.
But oh how irritating to miss an on-top-of-net volley. The whole court sits there, wide open, and you hit it in the alley-when midway between the sideline and centerline would've done well enough. (Experience provides you with an awareness of where the court really is).
Have you noticed the correlation between good demeanor and good play? The best players relish the game's difficulties. Mistakes and losing are inevitable. It's attitude that matters most - how one deals with failure, since that feeling of discouragement makes competing impossible. (Some young players cannot deal with pressure that is burdened on them; usually by well-meaning parents.)