kay don't think too hard on this and don't drive yourself crazy, I've been down that road too.. it does take some control over the conversation and MommaDeb is right, learn to be a listener.
I've done that myself, give out too information and realized later I regret it. However, in time with becoming a listener, you can "feel" what that person is like and understand what to say and what not to say. Also, you will be able to realize who to trust and who not to trust. (since I work with the public everyday, I have some experience in that field). I find myself to be a good listener, but if I want to chip in my 2 cents, I won't keep quiet.
I feel I am strong in knowing what I say is right and true, and I come across that way so people don't think I'm stupid or false in my statements, and yes, sadly I believe the honesty part does have a bit of something to do with Straight