One method for attaining joy is by contemplating G-d's absolute Oneness, meaning that even in this world, He is present. By doing so, we actually fulfill the very purpose of our existence which is to provide G-d a "dwelling place" in this lowest world. Thus, our joy is double and redoubled--we are happy that He is close to us; He is happy that He has a dwelling place in this world; He is happy for our happiness; we are happy for His happiness.