Our belief systems about love is vital as well. If we are only committed to romantic love, then we are committed to a mutually reciprocal Eros love system, which is initially a 100/100 system. It still works as a 50/50 system. But the danger is when love hormones get depleted or commitment wanes in the face of stress, then our commitment could drop further to 45/45 and eventually collapse.
Below: wiki extract about love hormons
A mirror neuron is a neuron that fires both when an animal acts and when the animal observes the same action performed by another. Thus, the neuron "mirrors" the behavior of the other, as though the observer were itself acting. In humans, brain activity consistent with that of mirror neurons has been found in the premotor cortex, the supplementary motor area, the primary somatosensory cortex and the inferior parietal cortex.