whether or not I take my night time medicine depends on what my BP is that evening.
What medicine did they prescribe for you? I've never heard of a BP med that you take only when your BP is high. BP meds have to be taken over time to get the benefits. They're not like aspirin or Tylenol. I'd get a second opinion on the medicine this doctor prescribed for you and tell this second doctor, how the first doctor wants you to take it.
The only med I can think of that a doctor would prescribe in that way is Hydrochlorothiazide, because that's a diuretic, which means your going to be up a few times during the night peeing. But if your Systolic was over 200 and your diastolic was over 120, then I hope that doctor gave you other meds too.