I think it's actually mentally self-protective, to not be able to imagine horrible things happening, because it's like the polar opposite of ptsd. But in the face of evidence requiring action or prevention, unwise to not accept what's there or increased probability.
I think young people, in particular, don't realize things like surviving but markedly (possibly) losing lung function for life, is huge. :(
I do believe people in general are known to not change behaviours with a lot of fear; somewhat with a little fear, and to the greatest degree when things are presented as the change will be positive/ help them.
But in the midst of fear, I think it helps to have clear directions, and for those that won't comply, try to avoid them. Someone told me matter of factly, who survived WWII, ~'those who listened lived, those who didn't died'.
In the meantime, don't panic, wash copiously, especially more so repeatedly touchable surfaces (door knobs, phones, taps, remote controls etc), keep your shoes separate (they can track much, so at the store take them off right away at home, disinfect your floors), limit close contact to people using their sense, mask and don't touch it, get rest and eat well if possible, exercise that you enjoy, nature +/ or family, look for comforting things/ people/places, pets, distance of course, but remember too context means a lot- a bar or nightclub is different than a store, and outside reduces risk. Most cases involve people coming in from hotspots (the carriers), lack of impeccable hygiene (required), and communal living space/ close quarters (including sharing food/ utensils, or bathrooms). Think of preventing colds and the flu- but ramp up your precautions like it's on steroids. And then keep going and do what you can to stay as healthy as possible, and as peace-filled as possible.
We have been very fortunate in general, relatively speaking, in that the generation prior experienced Smallpox, TB, & Polio epidemics, WWII (if not WWI), and the Korean and Vietnam War, let alone the height of the Cold War, and the Great Depression, to name just a few horrendous things. And they survived & had lives (again). We have been able to take some things for granted. On the upside, the environment (which most were/ are worried about) is getting a reprieve from unprecedented consumerism/ production, pollution, travel, and use of natural resources. Not the way we'd want it to be- but I remember hearing before this by a month or 2, "Well NO WAY will people reduce their air travel".
Keep yourself as safe as you can. I think the isolation has gotten to most people, too. and they're reacting more than thinking. :( All JMHO though.