There are two ways of living. One is ' Sangharsh ' -struggle and the other ‘ Samarpan ', which means surrender. Samarpan is not a helpless surrender like the surrender of the defeated in war, it's surrender with awareness and active acceptance. Struggle is to be ahead of others; to have more than what is given to us; to have something different than what we have. On the other hand, Samarpan is gratitude for every living moment.
Krishna says (3.16) that "one lives in vain if one rejoices in the senses and doesn't follow the wheel in motion." It's a life of struggle for someone on the path of satisfying these senses, which can never be satisfied. This struggle brings tension, worry and misery which is living in vain.
Krishna explains the wheel of existence (3.14) using the example of rain. Rain showcases the wheel of selfless action of water which evaporates and rains selflessly. Such selfless action is the source of supreme power (3.15). Following the wheel of selfless actions is the life of surrender which makes us joyful and gives us bliss.
Krishna (3.17) says that "the man who rejoices in the self ( atmarathi ), is satisfied with self ( atma-thriptha ) and is content with self alone and for him no duty exists." This is life independent of senses where one doesn't have separate desires than of existence. It's the pure acceptance of whatever comes our way while performing selfless actions. No desire, no duty. For him (3.18) there is no interest in what is done or what is not done, nor does he depend upon any being for any object.
Content with self is a common thread in the Gita which is also rejoicing in the self ( atmarathi ) and satisfied with self. When one is content with self, there are no complaints nor comparisons about our entitlements and capabilities.