being heedless??

i'm frustrated and having a hectic life.....again~ duh~~
i am wondering.. how could someone able to cheat and 'touching-fish' from others and yet they still can act like nothing happened or not their faults??? and even...think that they are not wrong at all..???
some others still keep on giving the advice to you..and on the other hand they had done something that u have never ever think that they will do something totally out of your mind??!!!
well.. i agree that i'm being headless and easily trusting other people~!! although someone keep telling what they had done and the worst ever things that i've done was that i'm protecting them and keep try to 'brain-wash' them..!!and that i thought that is my sister fault being so curious just like a cat!!
anyway..now i know that i have wrong trusting to the "leeches"..
so advice to all..
never ever trust anyone unless u really know who they are and what they are likely to be!!!