Cherish your life, don't waste your days or the time with people you love, because it's fleeting, unfair, and much of it out of your control. This is the uncomfortable truth of it, there is a pity for any creature with a mind that can comprehend death.
I have heard many skeptics compare death to the nonbeing you already experienced, you don't mourn the ability to live in Ancient Rome, to be a hunter gatherer to live as a feudal knight-and so you won't be able to mourn the future beyond your life. I will say that I don't find this fully satisfying, as once you are invited to the party it's hard to leave and have it go on without you. There will be no pain, but the end usually comes before we desire.
Knowledge is a gift with a cost. Being unshackled from religions pretty and ugly lies doesn't allow you to dwell in their comforts at a time like death. And it is a comfort, there is no religion I've seen that doesn't offer comfort in death. I think that's one of the key reasons they come to be. Particularly for those religions with a heaven and especially for those people in your life with a shared faith, death is a see you later, not a goodbye.
But I don't envy being persuaded by these ideas. I welcome the truth and face that reality as it comes. If this is it, then it's that much more precious. This life isn't a vapor on the wind, a forgettable wisp in a chain that lasts eternally this life is what you get. You have the opportunity to live for today and tomorrow, not for love of a heaven or fear of a hell . Not to please a god who designed you for his purposes, not to become a god or be one with god. To examine a religious life when religion is untrue reveals a great deal of lost opportunity and wasted time.
I find this opportunity invaluable, this truth a prize with a cost. This massive universe isn't set up for our benefit, but we get to experience it, and to our great fortune there is joy, fulfillment and happiness to be found there for most of us.