The significance of the trait of gratitude in Torah thought is very apparent. Three times a day we thank Hashem in the 'Modim' prayer; every time we eat, we thank Hashem for providing us with the food. Also, in the realm of bein adam lechaveiro, there is great emphasis on showing gratitude to those who help us. The mitzvos of kibud av v'eim and kibud Rav, for example, are largely based on a recognition of how much are parents and teachers have done for us. Yet it is no easy task to retain a constant feeling of hakaras hatov for all the kindnesses that Hashem, and, lehavdil, other people do for us. How can a person develop himself so that he excels in this most important trait?
Rav Noach Orlowek shlita, says that the single most revealing text about gratitude is the Haggada that we read on Seder night. Numerous halachos pertaining to the mitzvo of recounting Yetsias Mitzrayim teach us about how to attain the trait of gratitude.
In order to fulfill the mitzvo of recounting our leaving Egypt, the gemara tells us that we must begin by mentioning the 'genus' (bad) before we begin talking about the 'shevach' (good). There is a machlokes as to what exactly this entails; Rav says discussing the 'bad' means that before we begin thanking Hashem for taking us out of Egypt, we must first mention how our ancestors originally served idols. Shmuel argues that the 'bad' refers to the initial slavery that we suffered in Egypt before we left. We appear to pasken like both opinions, because both aspects of the 'genus' are in the Hagaddah. It seems that both opinions teach us a fundamental lesson about how to develop a proper feeling of gratitude.
Shmuel's opinion that we must begin with the slavery teaches us that in order for a person to feel truly thankful for everything he has, he must first be able to contrast his present positive situation with the past suffering that he endured. In order for us to truly appreciate Hashem's chesed in taking us out of Mitzrayim, we must first focus on the terrible suffering that we endured in the slavery in Egypt. By doing this, we can avoid the trap of taking for granted the physical and spiritual freedom that we experienced after leaving Mitzrayim. So too, in our daily lives, when things are going smoothly, it is very easy to forget what Hashem has done for us, and how He continues to constantly protect and sustain us. For example, when a person's financial situation is stable, he naturally may take for granted his situation and refrain from sufficiently thanking Hashem. However, were he to think about the times when he did not know how he would support himself, it is far easier for him to contrast his past difficulties with his current security. This should help him feel gratitude to Hashem.
It is less obviously apparent how Rav's explanation of discussing the 'genus' inculcates us with the mida of gratitude. How does mentioning the fact that our descendants served idols bring us to a greater appreciation of Hashem? It seems that one of the main factors that prevents a person from showing gratitude is a sense of arrogance. A person who feels arrogant will have an attitude that he deserves all the kindness that Hashem, or people, bestow upon him. Accordingly, there is no 'hakaras hatov', recognition of the good that others have done for him. He does not feel that they have done anything special, rather he has every right to expect them to serve him. In contrast, a humble person feels that he is not deserving of anything. Therefore, he views anything that is done for him, as a particularly kind act, therefore, he truly recognizes the good done for him. With this understanding, we can explain how reminding ourselves of our former lowly state can bring us to a greater appreciation of Hashem. We acknowledge that we are not great people with tremendous yichus, rather our heritage is nothing to be particularly proud of. Moreover, we acknowledge that any spiritual accomplishments that we have achieved are due to Hashem's chesed. when we say in the Hagaddah, "From the beginning our forefathers worshipped idols, and now HaMakom [Hashem] has brought us close to serving Him." By stressing our humble background we make ourselves far more able to properly appreciate kind deeds done for us.
Rav Shlomo Brevda shlita points out that he knew many Gedolim, each one greatly different from the other. However, one trait that they all possessed in abundance, was that of gratitude. This is perhaps because they all felt so humble that they viewed themselves undeserving of anything done for them. May we merit to emulate them and grow in our capacity to show gratitude to other people, and, most importantly, to Hashem.