When you wonder if you might be going any moment, you try harder to do what you want to do most.
It's easy to get morbid, depressed or fearful when considering the Big Dirt Nap, but one way or another you have to get past that, since the life you're living is a limited-time offer. Sometimes you may go for long periods denying or forgetting the essential fragility of existence. Then something reminds you. It might be a specific thing or the notion might simply cycle to the surface of your consciousness.
Fear not the death, since there's no point to that, but instead rebel against the preventable waste of time. At the same time, remember that the joys of a nap are as legitimate as the triumph of composing a symphony. Enjoying a good meal, you provide an essential service to the person who worked to prepare it. We can each only do so much. Frantic striving for achievement is not necessarily a better use of time than relaxed appreciation of every opportunity not only to exert toward a goal but to enjoy the efforts of others or simply observe the existence of all things.
Just remember to appreciate it. Humans are peculiarly equipped to be able to do that. And who knows? You may be called upon to provide a review.
The thing about living forever simply reminds you not to give way to impulses that could leave things in a tangle for yourself or parties on whom you have no right to impose. To say more would enter the realms of good and evil about which so vastly much has been written, spoken and acted already. Look for the boundaries of your rights and responsibilities. Don't complain about having to color inside the lines, because you do get to decide where those lines lie. If you cross someone else's line, do it mindfully. Don't be surprised by consequences. Of course you won't live forever, but you might live inconveniently long if you blundered around expecting to be taken out before the blowback caught up with you or with someone or something you suddenly realize you care more about than you thought.