Stress increases the heart rate! (fight!/flight response)
A bit of stress can be good for you if it spurs you on to do things, but then there is prolonged stress which is detrimental to health.
According to scientific research the slower your resting heart rate, the better the implications for your health. Your heart rate varies during the day depending on what it is that you’re doing. If you’re standing, lying down, calm or stressed, afraid, and so on your heart rate adjusts to that (fight or flight response).
In December 2008, the Harvard Heart Letter posited that a slow heart rate may translate into a longer life expectancy. And individuals with fast resting heart rates were found to be more likely to suffer from diseases such as hypertension (high blood pressure) than those with slower heart rates.
This is because when your heart beats each pulse puts a strain on the walls of the artery. During the two phases of a single heartbeat, blood is forced out of the heart and through the arteries, and filled with blood again in preparation for the next beat or contraction. More or fast beats give arteries little time for blood refilling which can lead to imbalances between the heart cells’ demand and supply for oxygen. This in turn leads to serious heart diseases which include diastolic heart failure (a symptom of the heart with no time to relax).
So rest and relax to enjoy more beats!!
Sources: BMJ, Harvard Family Health Guide