Tzaddikim's wholeness in every life-stage

ורש"י ז"ל כתב שני חיי שרה כולן שוין לטובה.

And Rashi, of blessed memory, wrote: "the years of the life of Sarah" — they were all equally good.

The Sefas Emes opens with Rashi's comment on the repeated word "shnei" (years), that all of Sarah's years were equal in their goodness.

כי הנה יש שינוים בשנות האדם ויש מעלות בזמן הבחרות ויש כמי כן מעלות בזמן הזקנה.

For behold, there are variations in the years of a person's life — there are advantages in the time of youth, and there are likewise advantages in the time of old age.

Ordinarily the stages of life each have their own distinct strengths, youth and old age each excelling in different ways.

אבל צדיקים התמימים נמצא כל מיני שלימות בכל ימיהם.

But with the wholesome tzaddikim, every kind of perfection is found in all their days.

The perfectly righteous possess all forms of completeness at every stage of life, not only the strengths proper to one age.

ובודאי אין זה בדרך הטבע רק מתת אלקים הוא.

And surely this is not by way of nature, but rather it is a gift of God.

Such uniform completeness across a lifetime is supernatural — a direct gift from Hashem.

וזה ענין ברך את אברהם בכל זאת השלימות שנמצא בכל מקום ובכל זמן בכח המלך שהשלום שלו.

And this is the meaning of "[Hashem] blessed Avraham with everything (bakol)" (Bereishis 24:1) — this completeness that is found in every place and at every time, through the power of the King to whom shalom (peace/wholeness) belongs.

The blessing "bakol" given to Avraham is this all-encompassing wholeness in every place and time, flowing from Hashem, the King of perfect shalom.

וזהו כולן שוין לטובה:

And this is [the meaning of] "they were all equally good."

Sarah, like Avraham, merited this complete and uniform goodness throughout all her years.

Summary: While ordinary lives have differing strengths in youth and old age, the wholesome tzaddikim possess every form of shleimus at every stage of their lives. This is not natural but a gift from Hashem — the same all-encompassing blessing of "bakol" given to Avraham, flowing from the King to whom perfect shalom belongs. This is why Rashi says Sarah's years were "all equally good."