Your face is a resident to 50 muscles and 20 of them are an expression muscles. The sole purpose of these muscles is to assist in expressing emotions. In order for those muscles to hold the face firm you need to use them.
If you can't laugh right now, I understand, but you can probably watch a comedy and brighten your mood instead of news alerts about the coronavirus.
According to science, the act of laughing or a simple smile can trigger a release of a happiness chemicals that can instantly elevate your mood. As a result you may appear more radiant and more attractive!
Dark circles are nothing else but tired eyes. The constant exposure to the blue light combined with hours spent looking into the screen of the computer weakens the eye muscles. As a result the undereye puffiness or dark circles form.
One way to eliminate them is to avoid the strain. Another is to exercise the eye muscles by looking out of the window as far as you can see.