Hi Garrett,
Not all theists view things the way you mention. After leaving the JWs I went back to my Jewish roots, and the whole idea of an afterlife and this life being futile, and that we have to prepare for the life to come after this--all those things got left behind.
Now I am not implying or recommending Judaism. It's not just a religion, it's a culture, and though people can convert, for the most part we aren't looking to add new members because we think people are called to make the best out of life and the circumstances in which they live now.
But I will say this. It was surprisingly comforting for me to discover that there was another way of looking at things. Atheists and other non-Jews can do the same too, and one doesn't have to give up their core values or adopt a certain theology or reject one--well, it might not be too compatible with Christianity and Islam now that I think about it.
Anyway, the view is that this may the only life we have, the one right now. And isn't it wonderful enough to be thankful for what we have now?
Why worry about preparing for a future day or afterlife? If there is a G-d, wouldn't it be a little thankless to be concerned about tomorrow when G-d went through all this trouble to build a vast universe so you can have today? And if there is no G-d, isn't it equally stupid to not rejoice in what we have now?
Did any of us prepare to enter into the life we have now? None of us had any control over being born into this world. If there is no G-d, then we are living the miracle of life now. Don't miss it. And if there is a G-d, well we didn't have to work to get into this life. Why would G-d require us to do anything to get into the next if there is one? If there is a requirement, then the Jews who introduced the world to this G-d surely never heard of one.
In Jewish tradition there is the understanding that this universe will come to a close one day and a new realm will replace it, a "world to come," Olam Ha Ba in our language. What is it exactly? How do you get there? Beats me. But you don't have to be a Jew or a theist or anything in particular to be a part of it. It is the natural order of things that has yet to be revealed, as natural as when a new day dawns. As long as people do the best they can, are just, and live to their full potential then they will naturally come to be there.
But preparation for it? Just as you have had no control in regards to entering this one, you will have no control over getting into the next. We do understand that those who work contrary to life and justice in this world won't be a part of the next, but I dare say very few I've ever encountered have anything to worry about.
If it doesn't happen, it doesn't happen. If it does, it does. I say if there is anything you are going to take from a theist, take this from us Jews who invented the monotheistic G-d: do your best at life now and enjoy what has been given to you now, and do the same tomorrow, and every other tomorrow that is given to you as long as they are given to you. There's nothing more to worry about.
Oh, and no belief in any G-d is required.
If there is a G-d, then life surely isn't about believing in G-d. Life would then be evidence that G-d believes in you.