All fifteenths of the months share certain qualities, most notably having a full moon. The feeling of being empty and down is very dangerous. Asher symbolizes how much we have reached and accomplished. Yoseph symbolizes the opposite, which is how much more we need to grow. Menucha (rest) indicates completeness and wholeness. Hashem created an amazing world, but Shabbos was the piece that was missing and that completes the world. Always do the best you can, but think that you never started and can do even better.