First of all, the blood pressure 120/80 is the AVERAGE normal blood pressure. in my med school books that's given as an average of normal values. The healthy range of blood pressure is between 90-140 for systolic (meaning the large number) and 60-90 for diastolic (the smaller number). Actually, by definition, anyone with a blood pressure over 120/80 is pre-hypertensive, meaning on their way to high blood pressure
. (though as states by someone else, all of these numbers vary by individual, someone can be perfectly healthy with a blood pressure of 130/90 or 95/65).
you are probably fine unless you have noticed a sudden drop in your blood pressure suggesting that the values given are not your bodies "normal and healthy" values. if this is the case you will probably be feeling dizzy and lightheaded a lot. if not, do not worry about it, you are perfectly fine.