the very last day

We have a mesorah, brought down in many different contexts, including the Talmud, the Kabbalah, Hassiduth, and I imagine also Mussar (though I don't have enough mussar experience to know for sure) but I personally saw it first, I think, in the Pahad David (Moadim:Shabbath HaGadol) of Rav David Pinto of Lyonne: One of the most potent weapons we have against the Yetzer Hara, the evil inclination, is to remind ourselves of the day we will die.

Often times we take this idea to mean that all of the pleasures of the physical world will be left behind. This is meant to recallibrate our relative valuation of particular actions and remind us that what we are about to do, although it will probably be enjoyable for the next few minutes, hours, days, weeks, months, or years, is ultimately something finite, and the price is much steeper than we are willing to admit.

That is basically the pshat, the simple understanding of the metaphor: scare yourself out of the craziness you are about to involve yourself in.

I have what I think is a new and slightly different understanding of the metaphor: Even when you know you want something good, to serve HaShem through life and eventually death, what is your death ultimately going to look like?

For me the answer is that I want my death to be as meaningful as possible, please God may it be at the end of 120 years. The only way my death can be that meaningful is if i've already made my life meaningful going into it.

Right now the way I see it is, if I gave my life today, how big would the kiddush HaShem be? Only HaShem can really know that, but would it be bigger if I did just one more mitzwah? Certainly.

So, when I look at the day of my death, it isn't a sad abrupt wake-up call to remind me of how fleeting all these worldly pleasures are, it's an alarm clock reminding me I have a date with destiny and I want to have time to properly present myself.

In the end, when and how I go is up to the sole discretion of He who created me, as R' Haninah ben Teradyon said, "It is better that he who gave me life should take it from me." Yet, whether I face that end a recalcitrant child who doesn't want to go home, or a refined Tzaddik with no wish but to serve HaShem however He wills, that is (at least partly) up to me.

starting from the end by looking forward

The Tzemach Tzedek, the third Chabad Rebbe, once explained:

"Study of Zohar exalts the soul; study of Midrash arouses the heart; Tehillim with tears scours the vessel. "

It's always nice to get a little insight into what we should learn, depending on our aims, our goals, and our personal character traits.. Obviously the Tzemach Tzedek meant that we should learn all three, but now we know more of what the gemara said, that Torah is a remedy against the Yetzer Harah. Whether your problem is with your body (ie. your vessel), your heart, or your soul, there's an appropriate remedy for it.

I just wanted to highlight the significance of Torah:
In the very beginning of Masechet Avodah Zarah, in the talmud, it tells the story of the end of days:

And HaShem comes before the world, holding a sefer Torah in his breast, (literally b'cheiko) and says:
"All those who involved themselves with her (the Torah), come and claim your reward."
And all the nations throng to him, looking for reward, and HaShem says, come one nation at a time, and the kingdom of Rome, the head of the nations, comes first. God says,
"with what did you involve yourselves?" Rome replies,
"Master of the world, we built many marketplaces, many bath houses, and gathered large sums of silver and gold, for no other reason than so that the Jews could study Torah." God answers,
"You fools of the world, everything you did was for yourselves, you made marketplaces to transgress there, you made bath houses for your own enjoyment, and the gold and silver is mine! You have nothing within you to claim this (Torah)" At which point the kingdom of Rome leaves inפחי נפש (I don't know how to translate that, but it's not pleasant) Next came in the kingdom of Persia (which the text relates to a bear) and God asks,
"With what did you involve yourselves?" Persia replies,
"Master of the world, we built many bridges, and conquered many cities and fought many wars, and all this we did solely so that the Jews could sit and learn Torah." God's obvious reply:
"For yourselves you did all this, you built bridges to tax their users, you conquered cities for power(?), and war is mine alone to make! You have nothing within you to claim this (Torah)"

[Then a lengthy discussion ensues whereby the nations debate with God about whether we, the Jews, kept Torah and how come we recieved it? It's really interesting, and every statement brings text from the Tanach to back it up. This was all my own translation, so please correct me if I made any mistakes. There were two words I didn't know how to translate but tried contextually anyways.]

The point though is that this whole dialog shows that in the end of days the only thing worth talking about is the Torah and its mitzvoth. The nations don't try and justify their actions saying that they were providing necesary services to feed the hungry or clothe the needy. They try to justify their actions by finding ways that they somehow have some secondary claim to Israel's relationship with the Torah. In the end of days, it is clear to everyone that the Torah is what is truly important.

Rebbe Natan (foremost student of Rebbe Nachman of Breslov) (in Likkutei Halachot on netilat yadayim shel shacharit) as well as the Pahad Dawid (R' David Pinto shlita from Lyonne) (in his commentary on Pesach and Shabbath HaGadol) and many others explain that the way to overcome the yetzer harah is to look to the end of your days. If you look to the end, you always see what is really important, seeing through transient matters. At the end of the world, the Talmud tells us, it is Torah that is important.