Is there a way to train yourself to sing and play guitar at the same time. I can do one or the other but when I try and do them together I f*ck up and can't play any more.

Or is it one of those can or can't do things?
Wrong forum...

Make sure you know the guitar part so well that even if you got amnesia you wouldn't forget it.

Start with easy guitar parts (basic rhythms) and try sing along, you will get better. James Hetfield didn't just pick up guitar, play Master Of Puppets and then start singing.