The Sefas Emes elaborates on this Midrash deriving an inspiring and empowering lesson. He quotes the Mishnah in Pirkei Avos that states: הַיּוֹם קָצָר וְהַמְּלָאכָה מְרֻבָּה - the day is short and the workload is great (אבות פרק ב משנה טו). The Tana is cautioning us that our time in This World is limited, yet there is much to be accomplished in the Avodas Hashem expected from us. Thus, the Mishnah is urging us to utilize our time in עוֹלָם הַזֶּה to its fullest, and not allow life to pass us by.
This Mishna may cause people to give up. Seeing the disparity between our time and required accomplishments may cause a person to despair of ever reaching his goal.
Remarkably, the Sefas Emes states that it is in fact impossible to reach one's spiritual mission, in this world, within the natural realm of 'time'. Life is indeed too short to be able to amass the amount of Torah and Mitzvos we are really supposed to.
It is this reality, says the Sefas Emes, that the Midrash is referring to. The Midrash is encouraging us. While it is not possible naturally to attain all our obligations down here, there is still a way to surpass this limitation. If one utilises his time in a proper manner, he will be granted 'supernatural days'. He will merit special blessing in his days and actions that will enable him to reach his ultimate goal.
This is what our Sages, in the Midrash, are teaching us. Since Sarah did her utmost to fill her time properly, she merited Divine assistance that enabled her to accomplish great things, ultimately fulfilling her purpose even in her limited lifetime.
So too, says the Sefas Emes, any individual who strives to fulfil his mission in This World, utilizing his time to the best of his ability, will also be granted supernatural strength that will enable him to achieve his goal, despite the restriction of his life-span.
The Sefas Emes bases this idea, on a tremendously profound concept found in Zohar. He teaches that just as one is allotted a specific time-span to live, he is also granted corresponding Divine days; he has designated spiritual powers that will enable him to achieve the 'unachievable'. The Zohar Hakodosh calls these days יוֹמִין עִלָּאִין - 'High days'. However, one can only access these strengths when he utilises his 'natural days' fully. Fulfilling their days with utmost perfection, is what enables the tzaddikim to connect with their otherworldly abilities where there are no natural restrictions.
Another way of attaining spiritual achievements that would otherwise be impossible is through doing teshuva. Teshuva can also allow us to merit this otherworldly power usually reserved for great tzadikim. The Baal Teshuva reaches exceedingly high - the Sefas Emes calls it the 'place of baalei teshuva' - which consequently opens up for him new channels to reach even higher in his avodas Hashem. Hence, by means of teshuva everyone can profit from this immense opportunity of יוֹמִין עִלָּאִין.
(שפת אמת תרלח ד"ה במדרש)