@Nep
Physical activities and counselling is good if one could afford/make the time and money for them.
More often than not you can always make time for physical activity. The fictional character in the manga obviously can also. It's just that people prioritize other things, not realizing that their body and mind NEEDS exercise and variety to function properly, and after they've slipped once they continue on a downwards spiral. That includes prioritizing tv, video games, internet, and yes - even a job, over their health. And sure enough this has consequences - you can literally die from complications caused by lack of enough physical activity, it's no wonder one would feel bad both physically and mentally when not fulfilling the basic requirements of their body.
Your problems start to look trivial after a good session of rock climbing, strenuous weight lifting, or just hiking in the mountains. Your mundane problems would be the last thing that's on your mind while squatting a weight at your body's limit, trying to find the next foothold while rock climbing, or just enjoying the view of that one frozen mountain lake while hiking.
The main issue is that people do not realize this, or simply decide to prioritize something else over their basic heath needs, which leads to a negative feedback loop.
Do yourself a favour and take care of your body - it's your body after all, and it's supposed to serve you for the rest of your life. They should really put physical activities above basic hygiene in terms of importance, so people would start to realize the importance of that. Your diet also strongly affects your mental and physical state. Needless to say, the typical western diet high in sugar and processed foods is garbage, and there is plenty of research evidence to back this up.
@Dizeros While I agree with you for the most part, I believe that drugs should be a last resort for when all else fails. There are enough cases of people killing themselves due to taking drugs that were supposed to "cure" their depression, that it's not even funny. Not to mention that a symptomatic treatment does not fix the underlying complex of problems. People however like low effort "magical" solutions to their problems, not realizing that those are not actual solutions, are only temporary, or have side-effects. The average person doesn't need pills to function properly.