[Furface]

Yes, we all need a challenge. 500 is a good one because we all like round numbers, and perhaps we can get a badge out of it!
But it does create massive hurdles in the old noggin. I'm sure we all - from beginner to international - have experience of "If I just shoot an average of n for my last three, I'll...." only to shoot an average of n-1. Or even "If I get a 10, I have the Olympic Gold" is the mantra of the Silver winners through the ages. The answer is ignorance. If you know the barrier you're hoping to break, don't look at your score or let anyone tell you (then, when you succeed, it is not an anti-climax). If you don't know the barrier ("What is the 1st class score for a York for Girls Under 13?") then don't look it up.
Unless you want to practice mental toughness rather than scoring....