Patience, mostly. I had a cat like that, once. He was rescued from a litter in which his siblings were slaughted by a farm dog. As a result, he was constantly on edge, mostly around strangers. Poor bastard. Over time, the tension and stress waned, particularly around us (context dependent). He was shown lots of love and care and became a core member of the family (and I'm not generally known as a 'cat person', whatever that is).

Give the cat patience and love and time, mate.