“Love doesn’t die a natural death. Love has to be killed, either by neglect or narcissism.” ― Frank Salvato
A bird with one wing can not fly.
A relationship (business, friendship, or other) needs two people both working at it, two wings overcoming the resistance of the air and balancing the stresses to be able to get off the ground and soar.
When one party does not care, or only cares about themselves, the bird can only spiral downward.