Continuing in the מאמר, the רבי fuses together the explanations of זהר and רש"י on "שני חיי שרה" in the opposite way as before - through "כולן שוין לטובה" one can reach "דילה הוו חיין":

When the source of מלכות is revealed, not only do the other ספירות benefit from it, מלכות itself becomes redefined. Instead of selflessness (ביטול) in contradiction to expression, מלכות can now express itself selflessly.

In our עבודה this means the ability to feel joy: not in contradiction to our selflessness to Hashem, but on the contrary - expressing it!