Lenin

red-rider,
First order of business is to replace the Diovan. I don't get any control from an ARB either so I understand. In fact, I wouldn't even waste the money by taking something IN ADDITON to Diovan.(Of course that's what your doctor will try to push...make sure the HCTZ Rx is separate !)
I am in the large minority, maybe 25%, who are "salt-sensitive" or "low-renin" hypertensive and if I treat my low renin with something that blocks the effect of renin I get SQUAT in BP control! I must either limit my salt (diet) or force it out (diuretic).
I choose the diuretic which is cheap and easy.
For people like us (if indeed you are low-renin) thiazides work like GANG BUSTERS... give HCTZ it a try, maybe 50 mg. once a day, and see what numbers you get.

No, the OCCASIONAL foray slightly over 200 won't blow an artery, they are pretty flexible, or we would all be dropping dead when first someone goes BOOO or the stock you bought yesterday goes into the toilet today...of course, with an aneurism all bets are off.
It's EXTREMELY damaging over the long haul though and if you are seeing these spikes with regularity (like more often than once a month) it behooves you to take action to get your BP lower. Get some thiazide and sell the Diovan on e-bay!