Regardless of the sins of the generation in the wilderness, this generation was considered to be the holiest of all other generations. Although they sinned numerous times, and the Torah criticizes them over and over, we must recognize that because they were on such a high level, Hashem had higher expectations of them. Even though they complained and sinned, they continuously maintained their high levels of emunah- faith/commitment- for Hashem. Moreover, Bnai Israel never truly complained, at times they just let their yatar hara- evil inclination- get the best of them, but they were immediately able to overcome those negative motivations and serve Hashem with utter faithfulness and joy.
At times, we all complain about our lives and may be displeased with certain circumstances. However, we must look to the generation in the wilderness for guidance. Just as they were able to overcome their evil inclinations to complain, we too, can learn to overcome our desires to ‘kvetch’-complain- and cling to our Source with utter emunah.