School Blood Pressure Lab, stress to relaxation difference?

For a lab for school we had someone think of a stressful situation for about a minute. Then we had to have them do some sort of relaxation exercise, like deep breathing, for five minutes. Their blood pressure didn't rise very much when thinking of that stressful situation. When doing the relaxation exercise it lowered most the way, but it didn't even rise 10 points in the first place. Why didn't it rise much? Is that what it should do? Why is the reason it lowered other than the person wasn't so stressed anymore?