This ain't gonna help much right now, but this is one of the reasons why the first thing I do with every new student is make them come up with a 5 minute 'showcase' piece.
Something that spans all your best talents that you practice on a daily basis and you continually work on throughout your life.

Whenever somebody asks you to play something, you just play your showcase piece. Basically, you should have it practiced so often that even though it's complex and impressive as hell, you can probably play it in your sleep.

If you really want a challenge, try doing multiple things while playing your piece. Like reciting shakespeare or singing a Britney Spears song... just dumb stuff that makes you laugh your head off.. but at the same time, trains your brain and fingers to effortlessly play without conciously thinking about it.