This thing ought to have a name, Sunday Night Syndrome, or Monday Morning Mayhems, because it is so common complaint with sufferers, that you make it thru the week fine, then Sunday nights your anxiety is heightened, by Monday morning your in absolute overload. It is heightened hypervigilance with the anxiety, and will magnify, breathing techniques will help. But Mondays were awful for me to go back, I was finally advised to take an extra pill (I was prescribed a benzo)on Monday's as soon as I got out of bed, it helped me to make it to work. Then Tuesday and remainder of week I would be fine on my regular dosage, bam Sunday nights roll around again same thing. Hard to explain to someone who says, well you've had a relaxing weekend, what are you possibly nervous about, I knew it wasn't the office itself, nor anything major, just was panic. Once your medicine starts working it does start the desensitization period, and that takes more than a week. I think that is the stage you are at, relaxed on off period, yet still sensitized to symptoms.
TrishE