playtesting yourself is real important, you can usually identify flaws, and dud games quite quickly. But what is important is that you have to learn to be honest with yourself; when you playeest with others often you find yourself defending aspects of your game against criticism, which is okay as long as you listen, but when you are by yourself if you ignore your own criticism you blind yourself to your games flaws.
to playtest others it helps to change your style, such as with one imaginary player you can be particulalry aggressive, with another particularly defensive.
now you just need to flirt with schizophrenia to get it right.
