The Buddha said that there are eight sufferings in life: birth, old age, illness, death, separation from love, long-lasting hatred, not being able to seek, and not being able to let go. I think the four sufferings of birth, old age, illness and death are human nature. Love and separation, long-lasting hate, not being able to seek, and not being able to let go, these four sufferings are love.
There are four stories in total, which respectively describe the four sufferings of separation from love, long-lasting hatred, not being able to ask for what you want, and not being able to let go.