During your life there will always be people you can trust. Those people may change at some point and that trust might dissipate but that doesn't change the trust you had had in that person. After the change has occurred there might be a mistake made by that person because they feel betrayed and they reveal or do something to anger you and hurt you because they betrayed your trust. So pick the people you trust wisely other wise you might be hurt. There are also people you could put the blame on that it wasn't there fault. That is not ok. If you do so you need to take a little bit to think whose fault it really is.
