(And of course, that is one problem with religions. There are dozens of mainline religions in the world, and each has dozens of sects within it. Each sect believes that all other religions are false and that theirs is the only and only true way. If so, a lot of people - the vast majority of the planet - are going to hell. So if you go the religion route, be sure you pick the right one!).
(Some folks find solace in rearing and raising children. This is, indeed, one way to become immortal, provided you do it correctly. The vast majority, it seems, sort of have litters of children and treat them indifferently, and then wonder why they are estranged from them later in life).