I'm not sure how existential depression can be easily fixed. At the end of the day, oblivion and the black emptiness of your consciousness simply being gone forever can indeed be hard to shake. I felt this way too for a long time as a very young child when a couple of my relatives died.
Unfortunately, I"m not sure what got me out of it. Perhas the fact that I could do nothing about it (at the time) anyway so why beat myself up about it. This is the saddest part, ruining the existance that you DO have right now, worrying about not existing later.
Do what you can now to find the religious and spiritual beliefs that you can believe in (if not your current set) and take comfort. If you're lucky, it will also show you a path to EXPERIENCE things now that will alter your "beliefs" about what's next.
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MeditationExpert.com
Stephen
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