It is a process, the "getting over" your expectations, so be kind to yourself. You've most likely have had these expectations built up over a lifetime. Long after your son has "deschooled", you'll likely still be deschooling yourself as well. I know I am, and I never have sent my kids to school nor wanted to. I have been philosophically in-line-ish with unschooling for about 5 years now, and I still find myself struggling with my own public-schooled expectations.
I'm guessing your son is in middle school? You might have a harder time letting go, because it seems to me to be the age that parents start panicking if anything seems "behind" or resisted or ignored. With younger children, it is easier for a parent with confidence to just kick back and take the long view of things.
Parents of older children probably have better, more specific advice, but I would first take the break that you are looking for . Give yourself that break, too. Maybe even set a date to mentally revisit your expectations and see if they have relaxed. Then, read some books, chat with folks in the community and online, observe your son, and do this while he is still in deschoolng mode. Maybe by the end of your own mental break, those fears and doubts will not be so overwhelming once you've had a chance to see your son outside of the school setting, with no educational expectations. At least you'll get a clearer view and operate less out of panic and more out of understanding.