There's an old chestnut of a story, where a powerful King
(some say Solomon) searches for
an artifact- or may just a bit of wisdom- that would make
a sad man happy and a happy man sad. One of his servants
brings back a ring inscribed with "This too shall pass."
The Universe won't last forever. Nothing is forever, except for the fact that nothing is forever. Does this scare you? It shouldn't. By the definition of the universe, the nature of being, nothing can be more natural, more fundamental to everything.
But of course it scares us. As creatures who live only a few levels beyond their instincts, we like things to be consistent. Stasis might be boring, but predictable is safer than chaos. And we want to extend that desire for predictability for as long as we can imagine, which is forever.
It's not just our instincts that tell us to hope for eternity: our culture and religion do as well. I blame my years of faith for leading me to expect things-- anything-- to be able to last forever and ever, world without end, Amen. Without that mythology, I might be more able to accept the universe as science- (thoughtful, peer-reviewed, testable-hypothesis science, our very best way of knowing things about the world-) tells us that it probably is.