金剛經纂要刊定記 3.125

3.125

我能下。釋。意云：由計我故，遂起降住勝能之心，不覺喜動故不自攝。今經既云：「無一眾生得滅度」，無法得菩提，則不計勝能，故能對治也。

From "I am capable..." downward is the explanation. The meaning is: because of conceiving a self, one subsequently gives rise to a mind of superior capability regarding subduing and abiding, and without realizing it is stirred by joy and thus fails to control oneself. Now, since the sūtra says, "not a single sentient being attains extinction," and there is no phenomenon by which bodhi is attained, one does not conceive superior capability; hence it can act as the antidote.