Wrist question

How should your left wrist be? I got used to it being bent and I think that it's a bad habit. Should it be straight or can it be bent? By bent, I mean like your knuckles are almost pointing to the head.

Your left wrist should always be straight whether you are playing seated or standing. It's ok to temporarily bend the wrist to hit a chord but straighten up as soon as you can. There is a very real risk of developing carpal tunnel and wrist pain from playing long hours with a bent wrist.
Ernest