Someone may appear to be one of the nicest and most selfless people you could ever hope to meet. 
But hidden beneath the surface, there may likely be a simmering cauldron of conflict, rage and resentment. 
Like many who are extreme people-pleasers, they find it impossibly difficult to say 'No', and have an uncontrollable, almost obsessive need for the approval of others, irrespective of whether they are colleagues, family, friends or strangers.