To trust or not to trust... that is the question

I think I need some advice from anyone willing to give it.  How do you trust anyone after you have been burned so badly?  When you have been lied to time after time after time, and the forgiving nature you have is so easily taken advantage of?  It is who I am.  I forgive because I don't think I need to hold onto all the bad things that people can do to you.  How do you ever trust someone after that though?  I can't continue letting people take advantage of me.  My fear is I am going to analyze every little thing that someone tells me.  Look at it in all directions, and all the possible lies they may be telling me.  I am afraid I am going to sabotage anything good that I may come across because of how I was treated in the past.  I don't want to make the same mistakes, so how do I trust again????