Blood pressure is unstable and depends on many factors. Blood pressure during sleep is lowering. And on the contrary, it is increased in physical activities and stresses. To stabilize blood pressure, you need have a rest and calm down.
If you are healthy, your organism is capable to control blood pressure. c provide the full blood flow without increasing if you change your position from sitting or lying. But if these systems fail to control blood pressure, it is getting to be increased. At this moment only you and your doctor can provide the effective assistance.
The arterial pressure of 120/80 millimeters of mercury is considered to be normal (upper limit is 140/90).