I’ve two maxims that I think might take the pressure off you – and so often it is this self-generated pressure that creates the feeling that your mind is blank (and actually i can’t see that as a bad trait as long as you yourself can recognise it) and that you have nothing to contribute.
The first is that many people never realise that silence and listening is an extremely powerful attribute in any meeting. The way that this was expressed to me in my teens was that we should never feel any pressure to speak because it is better to have people wondering what it is you would say and why you haven’t spoken rather than to jump in quickly. It may be that you never actually say anything but some people will notice and at least wonder why.
The second maxim is that it is better to remain silent and be thought a fool rather than speak and demonstrate beyond doubt that you are.
To my understanding it is actually a matter of confidence as I said. No-one’s mind is ever actually blank as you will be listening, processing what is said (otherwise you wouldn’t have a clue what’s going on) but you can fool yourself into thinking that, as a mild form of panic. Your conscious mind interprets that as having a blank mind.
In some of my consultancy work, I focused on developing strategies – perhaps tactics would be a better word – for overcoming all the rather conflicting events going on in people’s minds when they have little confidence in themselves. Do look further into this either by searching on the web, where there is plenty of free advice, or you might have a glance at one of my books,. While the focus is on business, it readily applies to casual and friendly meetings – but your focus, whatever you do, should be on gaining confidence in yourself.