This is a very good question.
I answer most questions as well as I can, and would be as honest as possible in the things I said, but there are some things about myself that I would not share. Obviously I am not going to say here what those things are!! LOL
I consider some things in my life to be too personal to post on the internet, anywhere.
I have no issues with people who would happily post their life stories as long as they post no personal details that can be traced, as that is against the rules.
I also have no problems with people who like me withold certain pieces of information.
If I was asked for advice on this subject then I would say post ONLY what you would be comfortable with your worst enemy in the world knowing. If you wouldn't want them to find out, then don't say it, as you have no way to know who will read your post.
Yes there are times when I have shared something with someone and had it come back on me afterwards and make me think well I shan't be doing that again in a hurry, if ever. lol
Because of this I have bigger trust issues now, but I believe that is only because I trusted the wrong people to begin with. You know not everyone who seems nice actually is??

I am more careful now, and I am learning new things about dealing with people every day. Hard lessons some of them, but useful, and full of information that it really is better to know.