I suggest taking the week to think it through and then discuss the real issues with her. If she is genuinely prepared (and can) to make changes to address the issues then I suggest its worth sticking with it for a period.
Say, give yourself 3 months (that will fly by..) and promise yourself to make a decision then.
I agree. By my reckoning there was just under 1 hour and 20 minutes between your "Shall I quit?" and "I have quit" posts yesterday. Now, I appreciate that you will have considered it for longer than that and that things came to a head yesterday but your decision will seem just as drastic and sudden to your boss assuming you have not previously made your feelings known.
She is probably as eager to ensure you are making the right decision for yourself as she is desperate not to lose you. I'd say there's no harm in discussing your feelings, taking a bit of a break from it, and then, on your return, assessing whether the situation is likely to improve to your satisfaction. You won't be able to change the nature of the NHS and neither will your boss but until she is fully aware of what's troubling you neither of you will know if a workable solution exists.
It's also worth considering the grass on the other side. I know a job where you're frustrated and working with your hands tied isn't great, but, IMHO, working under an Omega 5 days a week in all weathers wouldn't be an improvement, much as I enjoy a little spanner wielding.
As eluded to in your original thread, I think finding a way to walk out at 5 PM and leave work at work is important too - for any job, even one you love.
I hope you have a nice break in Amsterdam and it gives you an opportunity to chill out a little and I wish you all the best of luck in whatever path you choose from there on.
Kevin