In the epistle that the author of the Tanya wrote after his liberation from prison, he discusses the idea as it is expressed in the words of Jacob: "I have grown small from all [God's] acts of loving-kindness.”
The subtle difference between holiness and the kelipah may be seen in people's reaction to worldly success, to the manifestation of God's loving–kindness.
In the realm of the kelipah, the more that a person receives, the greater he grows in his own eyes.
The more successful he is, the more assured he is that he deserves success.
But in the realm of holiness, a person's reaction is, "I have grown small from all [God's] acts of loving-kindness."
The more he is given, the smaller he grows in his own eyes.
This is not an obvious difference like the contrast between large and small or beautiful and ugly.
It is a very subtle one, which can be recognized only when God grants loving-kindness: whether one grows haughty and vainglorious-or more humble.
–Rabbi Adin Steinsaltz
From Learning from the Tanya, Chapter 19, by Rabbi Adin Steinsaltz