An often forgotten foundation of Judaism, is תיקון הנפש, fixing the soul. Every Jew is supposed to work at self improvement as long as he is alive. We are supposed to leave the world in a better state than when we came into the world.
The Rabbis are constantly prodding us along to get us to work on ourselves. They understood human nature and how to overcome human weakness.
One such example is the idea of הכרת הטוב, recognizing the good. We are taught never to overlook a kindness that someone has done for us.
Rabbeinu Bechaye said this succinctly. If man is capable of taking for granted or ignoring a favor that someone did for him, he is destined to forget the Chesed that Hashem does for us as well.
The inability to show appreciation when someone goes out of their way for them, leads to much negativity. He will not be able to recognize the innumerable favors Hashem grants him. This will lead to a feeling of entitlement. Everything is coming to him. And when things don’t come, bitterness and self pity come instead.
All of this begins with simply being aware and appreciative, when someone goes out of their way for us. This awareness, leads to good things. This lack of awareness, the opposite.
We must make this little תיקון of הכרת הטוב, in order to bring Hashem’s abundant blessings.