People are born differently and every one has different character. It depends on the character every individual put up. Having a difficult co- worker and the ableness of trying to handle and cope with them is has simple. All you just have to do is to study him/ her and know how you relate with them, knowing what they like and what they dont like.
With that you will be able cope with their characters in order to maintain good friendly relationship with them because you wont expect you boss to sack him or her for you.