Cognito - I am not sure that's quite what I'm putting across here. I obviously appreciate your thoughts but I'm not "just" talking about being private or "stiff upper lip" - I am of course :) but I didn't used to be: as a little kid I would wail when I fell in the playground or whatever 
I do of course admire my tendency to be able to carry on - it's got me this far - but just the same I don't want my life to continue as it has as while I have survived I have largely survived alone.
The reason I think you've misunderstood is this - If you'd like to be less guarded and more open, & if you think it's a problem, then all you really have to do is share something personal and answer questions honestly.
No, no x 1000 - that isn't what I'm getting at at all. I will happily chat away to people as evidenced here and one of my friends and I have a particularly bizarre friendship where we will inform the other of even bowel habits!
(There is a backstory to this!)
But, I lost my mum at 14 and I didn't cry then and I haven't cried since. Ditto with my dad. A few tears initially as it was sudden but then nothing. No tears over homelessness, the loss of a child (won't go into that) or a thoroughly misspent and chaotic youth.
Since having counselling I have remembered random remarks and comments, meaningless at the time but I remember someone commenting that I dealt with a difficult work situation by "disappearing" - I would go outside and read rather than engage with difficult colleagues at lunch; one friend said "you hold a lot back" when we were tipsy one night; one person commented that I'm a "closed book."
I am NOT saying I'm going to tell my life story to people but I know - I know - what they mean. It's a wall I've built for protection but now it's so built into me I don't know how to tear it down. It's preventing me really letting people in (even properly my lovely counsellor who has got closer than anyone else but it's still not there) and stopping me accessing the one thing I want which is a partner and family of my own.
Please, please, don't shrug it off; it's not talking to people. I can do that. But I can't feel, properly and sometimes I don't even feel properly human.