Even with our highly developed brain, humans will inherently be lonely. The reason is because no one can fully understand how another feel and what went through one's head.
This flaw will be greatly exacerbated by negative emotions such as jealousy and anger. We can try our best to regulate our emotions but there will be times where we fail to do so. This is why it is very important for us to be able to walk through our partner's thoughts and walk our partner through our thoughts especially after an emotionally charged episode. This will enable both to understand each other sees during the moment and let each other understand what prompted the manifestation of what they observed.
If this is done well, instead of drifting apart, each rift will become will become opportunities to get closer and have a better understanding with each other. I believe this could be done by the dominant naturally or through a pre-defined "ceremony" after things cool down.
No matter what happens, walk each other through each other's thoughts and you will walk together forever.