Easy. Just look at the chess player shortly after they win. You'll see a sigh of relief and a calm aura from then on 
Joking aside, there is some truth to the above. It is just that most chess photos try to capture intensity and competition and other things to hype the game in some way. It is kind of like how sport athletes tend to be shown in only the most dramatic of moments and during the pinnacle of a great play...they are human and don't play well other times, but the media will try to paint them in an optimistic light. This is the same with chess tournament coverage.
I sometimes look at photos or videos of tournaments or casual games to see what movies people make and how it’s organized. I noticed that almost always players display some degree of anxiety, pain, discomfort, annoyance, irritability, on their face and in their body. Maybe they lean forward and prop their head with their hands, maybe they keep tapping their leg, whatever it is.
It seems impossible to find players who show normal behavior, more or less relaxed face, and lack of anxiety. The only one I can think of who seems to be extraordinarily calm is Wesley So. Perhaps it is the positive effect of his religious views. Who knows.
If anybody can suggest a player whose photos or videos show calmness I would greatly appreciate it.
Why this is of interest to me is in part because it seems like people who play chess regularly over the board often seem to have issues with anxiety and nerves. I know, at least in my case that I suffer from this problem not just in chess, but in most things in life. I have ptsd issues from something unrelated to chess and I actually started to play chess to stop panic attacks from other things. To me it’s interesting whether any chess players consciously put in effort to stop nervousness and anxiety using something like meditation, breathing, or cognitive behavioral therapy.