Open and vulnerable versus closed and protected? This is a misunderstanding of what it really is like. For a start there is no 'closed and protected' there is only 'closed' - there is no safety in being closed, no protection in being closed, quite the opposite; to be closed is to miss the actual experience of being alive. There is no 'open and vulnerable' - openness, awareness, is the true strength, it is stupidity that makes one vulnerable.
Look, the universe manifests exactly the same whether you are open or closed. The same things rise up in front of you.
"Before enlightenment - get up, wash, light fire, eat breakfast.
After enlightenment - get up, wash, light fire, eat breakfast"
There is an awful lot of nonsense thought about what and where we are and what we should be - for instance, there is no place named Nirvana that we 'go to' - there is no path, no destination, no salvation, there is only 'this'. There is no 'getting better every day', 'life is a school', 'God is testing me' - none of that, there is only 'this' - and to live in this properly all one has to do is to wake up to the nature of reality, then you will see that most people are sleepwalking in a weird dream.
So, be open, always be open; be open to all that manifests - there isn't good and bad, there is only what manifests. Sure, some of it hurts but I can tell you that it hurts less if you are open rather than closed. R D Laing once said that "the only pain you cannot avoid is the pain you feel when you try to avoid pain" - and this is true.
Most emotional pain is simply that you have created a picture in your head of how you want reality to be and actual reality is different to that invention.
So be open, always be open .. don't write scripts in your head and then try to make reality conform to that ... just go with what is actually going on, without resistance.
But I am not talking about being stupid - being stupid has its own reward - one has to be wise - "as wise as serpents and as innocent as doves" - so yes, be open, and being open one is aware and when one is aware one can see and move freely within all this .. .. - and it isn't exhausting, it isn't tiring, it isn't difficult if one keeps grounded - being grounded and also not fighting actual reality.
As for the experience you felt in the middle of the night ... I do wonder how many Spanish coffees you have each day
- but the opening you had, one can indeed be troubled and it is necessary to stay grounded .. being 'open' isn't to do with allowing the mind to go off on a crazy tangent, it is merely to do with seeing things as they are and being calm and centred .... stay grounded - Buen Camino!