First stop and take a deep breath.
There are few important things in life and most of those are present in the moment. Therefore stop being so serious about everything. Sure you are important and whatever is it important, however if you are honest to yourself, is it really that important?
When we are under pressure, it means we have to deal with that pressure. If we choose to tackle it, our bodies and minds gets to a stressed state in order to deal with it. In other words stress helps our bodies and minds to prepare and deal with it. Stress in these cases is beneficial.
We are oscillating between stress and relaxation. Too much of either for prolonged time is no good. We should consciously also be mindful in which state we are and do we need to increase or decrease the stress for example.
We do not need to be stressed when we are about to rest.
We need psyche a bit up before giving a talk or meeting a client.
If we all would be zen masters, we could do this consciously at a right time. Since we are not, we have to learn ourselves to control our minds through our breathing or meditation for example.
Everything begin with breathing, so breathing is one of the most effective ways to tell our lizard brains should we increase or decrease the stress levels.
Learn to relax under pressure, and you won’t have another bleak day, because you know what is important and what’s not. Above all you are just in the state of mind where you want to be.