The phrase "as below so above" means that everything physical is really continuous with spiritual reality and therefore, has spiritual counterparts. What is below on the earthly realm metaphorically mirrors what above in the spiritual realms; it's just that the limitations of our capacity to perceive doesn't allow us to see whole entities. As a result, we can only follow any given entity with our eyes up to the edge of our perceptive limits.
Lurianic Kabbalah describes a cosmic event called "the shattering of the vessels". In the early universe, the basic primal spiritual forces, known as "sefirot", shattered - as they were unable to contain the spiritual light streaming into them. The light was simply too expansive for their rigid positions to hold onto. Being unable to serve as vessels to contain the light, they exploded. The shards of the explosion became the spiritual and physical building material of the lower realms. One might wonder whether this fragmentation seriously compromises the potentially seamless continuum between the spiritual and physical reality and therefore, brings into question whether the lower realms truly mirror their counterparts in the highest realms.
I'd suggest that there probably is some compromise. However, the lower realms still mirror the higher realms. Only, it's fragmented mirroring, as the mirrors (or lower realms) are fragments. Fragments can cause some distortion. Looking at one's face by loosely bringing together bits and pieces of a broken mirror doesn't exactly make for a great image. Obviously, more fragmentation means more potential for distortion. However, every fragment is still reflecting some piece of the image.
The cosmic repair work to mend the fragmentation is done through our prayers, good deeds and kindness. In response to our good behavior the Creator rearranges the material across the various spiritual realms and creates new spiritual structures. These newly reconstituted spiritual structures are called "partzufim" (which is the Greek word for "faces", as borrowed by Hebrew/Aramaic). Continuing with the mirror metaphor, when the mirror is put back together, then it reflects the full face, not a fragmented one. Maybe, that's why what's repaired is referred to "partzufim" or faces.
One of the Creator's tools used in this repair work is a new kind of light which He streams into the space of creation through the "line of light". Unlike the first light which streamed down the "line of light", shattering the vessels, this light is much higher and helps build and reinforce the repaired structures, so they don't shatter again. One might question, "If the second light is even higher than the first, how does it avoid doing damage?"
Rebbe Nachman of Breslov was fond of saying that the sickest patients require the most profound physicians. Since these patients are in such a fragile state, someone whose merely a "good physician" might ruin them. They need the best of the best. So too with the light, the highest lights have the greatest ability to deal with the most fragile situations. The first light is like the "good physican", whom though well meaning, ruined the situation. The second light is like the "profound physician" who brings a new depth of skill and understanding to heal the situation.
The "line of light" is the main cable bringing down spiritual lights from the "Infinite Light" into the space of creation. I think of it as a kind of cosmic spinal cord, which extends the commanding signals of "Infinite Light" into the space of creation. Before entering the space of creation, this new light needs to be filtered. Otherwise, it will overwhelm the creation. This filtering function is performed by the "line of light", as it controls the flow of light streaming into the territory of creation.
Based on this, know that everything you consciously think, feel and speak somehow affects how well our earthly realm mirrors higher reality. Being in full awareness of this, turns each and every moment into dearly precious opportunity.