To me, that’s the ultimate face of an existential crisis; confronting the reality of what our existence is. We’re almost unbelievably brief sparks in an endless darkness that didn’t notice our arrival and won’t notice our departure. What does it mean? Nothing really.
For some I guess the solution is believing that they’ll live forever in one way or another. For me it meant not thinking about a grim reality that saps joy from life, and just focusing on the people I love, the time we have together. It might not be ideal, but it’s what we have. What is an existential crisis? IMO it’s what hits when you when reality starts to seep into you in some small way. Maybe it’s mortality, or the absurdity and arbitrary nature of human endeavors, or something else.
Of course "existential" is a philosophical term. Heidegger, one of the great existential philosophers, famously used the day to day experience of humans in order to access the very nature of being - of existence - because humans are unique in that existence is a fundamental concern for them. Like when Satre writes in detail about the strangeness of door handles, they're something that we use countless times in our day to day lives, we just never notice them until they become a concern for us, like when they break.
So an existential crisis is just that feeling of unearthing something fundamental that's always been there, but now has come to the forefront for whatever reason.
Personally I believe there is only ever one existential crisis that we go through and whether we face it head on or just the satellites around it, its centre of mass is always that audacious fact that something exists rather than nothing.
BTW one doesn't simply answer this question. The resolution of an existential crisis is a new way of life, not merely understanding some standalone empirical fact about psychology or physics.
If the cause of questions is a lack of achievements, than it may be not the existential crisis, but something else.
Existential crisis is the good one, it means that you grown above your goals and now you can find new ones. But it feels bad, like any other crisis.
So achievements are any objectives, which are significant for the person.
The problem with this crisis is a relativity of the "lack of achievements". Life can be pretty good, but nevertheless worse than expected ten years ago. To be successful in my own eyes I need to accept my real performance in the real world, to rewrite my plans accordingly, and it can be a painful experience.
If you're not contemplating radical changes, you're probably not having an existential crisis.
[1]: http://www.davidsongifted.org/Search-Database/entry/A10554
I went from stress and anxiety to existential crisis.
Maybe this is too simple.
Maybe it's precisely this simple.