Is this true that we shouldnt?

reveal ourselves to people?in order that people doest take advantage on us?u mean we should always hide our own self and be uptight?and always acting ?because they said if people know us for who we are they tend to take advantages then,what should we do?acting all the way how long shall we continue to act as such?who can we trust if it is not our friends?but why do friends cannot be trusted?how do we know when we cantrust someone?