Do not hold your breath, sit straight, do not talk with your mouth full. You received plenty of those lessons way back in time when you were a snotty kind of person and you assumed, no, wait, you took those big lessons with utter conviction. Aren’t those interestingly simple ones? Does that mean anyone could be a parent? Ok, we are getting a bit off the track here, but what really matters is to learn to breathe the way you should, the way kids do when they laugh with their whole bodies. Perhaps you know the way which you picked up from your own kids already so now you can all laugh with your tummies shaking and sending that kind of roaring laughter high into the sky to make the stars fall. Why breathing and laughing?
Those two constitute two easy relaxation techniques which people often forget in their misery. But that is a damn right technique to let you absolve of most of the tension you generate during the day in your body. When a masseur is not around to offer you a pain relieving massage some deep breathing stolen from your break after or before a brunch could do a trick nicely. Or replace it simply with a hearty laughter, which is quite a challenging way to choose as we tend to forget what it means to have a good laugh here and there when we age, when things taste more sour than before. The ability to laugh is typically human, though with some exceptions in the animal world (apes obviously), but it is extraordinarily easy to forget what it feels like if your life eg. took the turn for the worse. It is a great practice for the brain too as thinking becomes easier once we have had a laughing fit, bursting out loud. Wry humor does not cut it, sorry. And stay away from black humor for a while, just do something silly for a change, now that would teach you something. When that feeling arises then you could say it is indeed refreshening.
With breathing techniques, the basic thing would be not to force anything just to let go and observe yourself as you breathe, then slowly move breathing to the diaphragm and move from there. Now that is the way babies breathe which somehow turns more shallow as we age. Some lost skills can be recuperated though, just need some time and practice in those crazy times. Whenever you feel at a loss, sometimes you inhale the air and that is deep enough, but you could benefit the most by reducing stress and strain through careful and not forced breathing. It should come naturally to you but you need to watch it and give it a few days before it becomes a habit. Think of this as an extra to your teeth brushing technique and some other ways of keeping your health in check.