Frequency and time of taking high blood pressure medication - Ask topic #3

I have 2 questions:

A) Prequency issue:

I don't take the medication my doctor prescribed daily. I have 2 ways of taking it when

1) I get a bit of hradache, and

2) I have the blood pressure measurement higher than normal

I heard that to make the medication work, I should take it regularly. Is there any harm if I don't take it regularly? If so, how much in what way?

B) Time issue:

I also heard that during sleeping, blood pressure goes up. So it is good to take the medication before the bed time. Is it true? Or is it different for individuals?