So, the thing about negative thinking is that it can spiral out of control. It feeds on itself. Unlike a perpetual motion machine or anything physical in this world that actually has to confirm to the laws of physics, negative thinking grows bigger and more encompassing the more it is done. When you have a group of people that aren't fact checking, aren't reality confirming, aren't thinking around the problem but just emotionally hanging out in the morass of negative thinking, it is so so so terribly easy to stay in that line of thinking, and fuck-you hate the world.
Which is not to say happy-go-lucky-let's-ignore-reality-in-favor-of-thinking-everything-is-okay positive thinking is great. Indeed not as such thinking is actually detrimental to developing resiliency because it hides checking reality and planning ahead.