How do learn to trust others again?

I've always been a little naive.Anyone was able to trick me with a sob story.Also I was,I suppose still am a lot gullible & I am a sucker for guilt trips.I always had this feeling that everything would be all right.like I haven't hurt anyone so why should someone hurt me.I hate it when people break promises & i hate it even more when they break the trust I had in them.I just survived a deep depression & 2 suiside attempts.I'm not intrested in suiside anymore.It seems weak now.but how do I let people near me again?I can see I am hurting them by my rejection,but I'm too afraid to trust again.Please help!!!