you don't have to worry about it, you know nothingness better than what's like being alive. As neil degrasse tyson pointed out we weren't even around to ask these questions for the 99.9999% of the cosmic history. I'll comment on these death of universe and earth discussions. First of all our solar system will be long gone before any of the predicted theories on death of the universe even begin to happen. Sun will become a red giant in around 5.4 billion years, that means it'll get as big as the inner solar system (sun to mars) but the earth will be long gone before that process, and human species will be long gone before earth is destroyed (We're actually on the verge of 6th mass extinction cycle on earth). The heat death of the universe as Andrez posted is just one of the theories that could happen as it's pretty hard to simulate billions of years we'll get there soon enough though.