<human>: Can you condense the text into three sentences or less?

As someone who is naturally very inhibited, and with social anxiety, this is the question I often ask myself. I have plenty of regret for things I never said; never expressed in the past. My cowardice has led to lots of missed opportunity, and looking back I think, "If only I had just said what was on my mind." 

As an attempt to come out of my shell, I've tried to stop doing that...and in some cases, ended up saying things I regret saying, and burned a few bridges. This is the case with both friendships and attempted relationships.

I feels soo hard to know. They say, "You regret the things you didn't do, not the things you did," but of course that's not the whole truth (I'm sure there are plenty of people in jail who regret the things they did). I'm thinking about sending a message to someone right now, with some thoughts I've had in my head for a while. I really have no idea if it's going to be a 'I'm happy I got it out there, I was so afraid but for no good reason,' or, 'God what an idiot I am for opening my mouth. I've totally ruined that relationship now too.'

You could say, "Only say things that aren't negative or hurtful," but that's not quite right either. Always holding back the negative leads to, 1. Holding on to a big bag of negative. 2. People not respecting you because you don't stand up for yourself when you feel wronged. 3. Not totally sharing yourself and developing really deep relationships where people know who you are.

So, what's the answer? Anyone have a good rule of thumb?
<bot>: Regret things I never said. Tried saying things, now I regret the things I said. How do you know when it's a good idea to express yourself?