Trust...?

i always thought it was easy to trust people. so i take everyone at face value. i have had a few jolts in life bt i thought that ws all a misunderstanding. but now as i'm growing older i find so many two faced people around me. in front of my very own eyes i have seen people change sides. someone who i considered a friend turned against me...bt behind my back. i hate backstabbers. why cant people be honest? and they pretend everything's fine bt as soon as u look away they'll stick a knife in ur back. sometimes i wonder if trust even exists today. how can u tell who's ur friend and who's a traitor? will i become a liar myself?