This is where understanding of the culture plays an important part in understanding the meaning of this phrase. A cookie is typically something small, sweet, and tasty. If you are not too hungry, eating a cookie brings a small joyful feeling to you, but not significant enough to make you happy all day. On the other hand, if you are starving to death, a cookie is probably not enough to sustain your life but rather it can induce a feeling of depesperate desire and want that make you feel even more hungry.
So my understanding of this phrase is that, life is personal and means something different for everyone, even when the "cookie" is the same.
