I think there is a wide variability in humans.
Some are very arrogant in their views and will not be able to adapt well to major changes (like would be caused by officially acknowledged alien contact).
Others will find it interesting but just carry on with their lives as normal.
Others will find it a wonderful challenge and rise to it.
The old Brookings Institute paper (around 1960) argued that the vast majority of humans fell into the first category.
That may have been true at the time but with modern communications humans have been exposed to a lot of stuff—including ideas they do not like—but at least know of its existence.
My read is that today’s humans (for all their issues—and there is a long list of those) are much more resilient (in terms of ideas and concepts) than their grandparents.
That very much depends on what "it" is.
On top of that, there may be no "normal lives to carry on" with. In other words, it might be hellish beyond our ability to comprehend.
Even the Bible warns that men's hearts will fail them for what is coming on the Earth.
We'll see. I'm not optimistic. If what's coming were positive, it wouldn't be so elusive.
And I've been routinely accused of being an optimist.;-)