Commentaries on this commandment usually focus on its Golden Rule aspect--to treat others as you would wish to be treated.
The Simple Explanation puts it this way: "In order for units of consciousness to join and work together for the greater good, they need relevant information (including shared meme chords), they need to be willing to channel coherence from the metaverse, and they need to love one another."
While we human-level UCs often struggle with loving others, many of us also struggle with loving ourselves, so how do we accomplish the Great Commandment?
In the article "My Self, The Governor of Whoville," I explain that my governing UC is associated with a veritable galaxy of aggregated UCs hierarchically distributed below it. "I" am not alone in this body of mine, but coinhabit this material space with countless other UCs devoted to instantiating "my" body. The commandment to "love myself" is a reminder to be kind and wise in the governance of the UCs that make up my Self's body. I am the ruler of their galaxy--I am the "Governor of Whoville" to borrow from Dr. Seuss. When I ignore the information coming "upline" from my aggregated UCs, my physical body may suffer emotionally and physically. If I ignore my aggregated UCs altogether, they are like sheep without a shepherd, and my emotional and physical body will surely suffer. I must be the wise ruler of this body, as it is my governing Self UC that is responsible for this little galaxy. This can be considered the essential rationale for loving myself. It is not my Ego I am loving--it is the Whoville galaxy.
If my Self UC cannot act with wisdom and love toward its own "mud" and meat, then how can it act with wisdom and love toward other UCs at the lateral level--its "neighbor"?
The "neighbor" that I am commanded to love is any unit of consciousness that occupies the same level of complexity as my UC. It is the job of every UC, no matter its hierarchical level of complexity and sophistication, to reach out laterally to others of its level, working together for the good of all. A sub-atomic particle's neighbor would be other sub-atomics. A liver cell's neighbor would be other liver cells. A human's neighbor would be other humans, but also other complex life forms. My dog is not a citizen of Whoville. My dog is my neighbor.
All of creation is called upon to work together with others of like kind for the survival and benefit of all. This is a Simple Explanation of The Great Commandment.