This is where you are basically forced to display a positive life. It makes you no longer authentic, or if you naturally refuse to follow this (which is expected!), you may feel bad. But it's all an illusion! That's why it's "toxic". Social media has to do with this, for instance, Instagram pictures. That is why I don't use Instagram. The only one I really use is YouTube. Looking at de facto positivity biased moments is no good for the human brain that inevitably likes to compare itself with other people.
In a society that only values positivity, the "doomers" feel doomed about the fact that they feel doom. It repeats... and even optimism feels like a lie now. And negativity about negativity, which only makes more negativity, continues... (even if the hedonic treadmill adapts, it still feels worse and worse every single day...)
When positivity becomes the societal norm, negativity becomes seemingly weird or an outlier. This may, in turn, make emotions like stress or anxiety even worse! This is likely because the environment does not really reward such emotions; naturally, some people get "implicitly" shamed at school if they aren't stoic enough, which is natural in early development. (However, this does not diminish the value of Stoicism) This only further strengthens this belief.
Through darwinism, emotions were really just responses to stimuli. The key here is "responses". Some stimuli, like those in school or other people, you can't really control. If an action occurs, responses may occur too, and that includes emotional responses, even sadness, even stress, is caused by that. Emotions is also part of your subjective reality; trying to suppress reality is totally futile. This is exacerbated by the fact that most places, even if they claim to be accommodating, do not actually accommodate for disruptions! Having loud noises at school would get you sent straight to "intervention". This further shames them.
Not mentioning bad things DOES NOT make them less common. Support is denied. Even most support cannot do much. But denial is WAY worse! For instance, suicide or school slavery or violence. Suicide is more common than homicide yet way less talked about. That is the availability heuristic.
Where schools try to suppress negativity, calling it disruptive and
such, or it may be the fact that the examination system is
here to stay regardless of how negative you feel about it, which implies
a dismissive "Deal with it!"
Personally, it may also come from the fact that the younger generation
is not that actually accepting of negativity in general (or are
conditioned by social media optimism, or became apathetic in
doomscrolling things that cause pessimism), and
feel like they need to say something positive to help out, which doesn't
help if the person wants validation of advice.
They exist. Just like Absurdism's conflict of meaningless and human life, the conflict between the ideal positive state and reality exists! But it cannot really be fought. So the only solution may be to accept it as a result of determinism. And then, honestly, the hedonic treadmill may return you to normal soon after, for some circumstances.
Try to release negative emotions in an isolated room for fear of disruption. Perhaps in bed. It may take time to process emotions. You can try to talk to people you trust, but the only things I hear are silver linings that don't even answer my concerns. Rather, radical acceptance, as said above, is probably much better! Detachment rules! Always!
Often times they are too insignificant, yet people act like you are irrationally pretending they don't exist, even though the reality is that silver linings are by definitions pretty small in comparison.