If very high blood pressure can be a symtom of white coat syndrome, how can it be controlled? One says--do not try. Hmm?

True "white coat"? If a person only has measurements of elevated blood pressure at the clinic, but normal measurements at home, at work, and during the stressful moments of his day, then he is likely ok. However, if he tries his best to check his blood pressure during times of stress (not relaxed on the sofa), and keeps a record of all the measurements, and many are elevated, then his doctor may want to treat him.