Transition to poker

Hi
I am just wondering how many of you have made a transition to poker?
I am a red chipper and on my last casino trip i played 2-4 hold em and lost 200
I have read the books that were recommended on here for low limit games by Lee Jones and Slansky

When I play BJ and lose I know that it is part of counting and will come around my way however Blackjack really is a science while poker is an art with science mixed in

Without getting my ass kicked what is the best way to know if I am a good player without losing a ton of money

Did most of you lose when you started out?

Thanks a lot