Hakaras hatov is commonly mistranslated as expressing gratitude. That is not what the words mean. Hakara means to recognize, to identify. Hakaras hatov doesn’t mean expressing gratitude, it means recognizing the good in your life that deserves your gratitude.
The importance of gratitude in Judaism is paramount. The reason is that the Torah wants to teach us the importance of perspective. I once heard a beautiful thought about the words we say in the prayer of Aleinu – “In the sky above and the ground beneath.”
The obvious question is about the words “above” and “beneath.” Are they not redundant? We know the sky is above and the ground is beneath. The lesson is that when it comes to things “in the sky,” that is, spirituality and important things in life, always look above and strive to be better. And for things “on the ground,” like health and wealth, always look beneath and realize it could be so much worse.
Life is about perspective and that is why hakaras hatov, recognizing the good, is such a central concept in Judaism.