This extends to any type of business or co-worker relationship, but Scrum teaches truthfulness above all else.  The Team must trust each other and be honest with themselves and other Team members.  If you have a problem with a Team member, talk to them.  If you see a Team member struggling, help them.  Let it all hang out at the retrospective.  You can’t move forward unless you are honest.  Sounds hokey, but business is business, nothing is EVER personal.