It is quite common as the reality of the situation takes a greater hold but because it is a roller coaster you may find that this is temporary -you go back to managing then it hits you again but each time it does it isnt quite as hard or as long lasting as the last time.You may also find when you are actually at work you do manage -its when you are away from it that you breakdown and then as part of that, begin to fear and build and build anxiety too a point where you think you wont be able to do your job properly without that being the reality.
I have spent time crying in the toilet or behind the shed but was able to then carry on and continue working -i think it helps if you have in mind a place to escape too and take a deep breath -and knowing it is there this then lessens the anxiety and you need to actually do it less often.Also go out in your lunchbreak a quick walk round the block can work wonders.
I found this place helped not only because people here do understand, and because you can sometimes speak to total strangers more candidly than those closest too you -but also just the act of writing those feelings down helps.I hope that this site will offer the lifeline it offered me.