Vivien's Neverland

I read this short story written by Doris Lessing today.

This is a story talking about the effect to a woman in a marriage.
This is it. Susan and Matthew Rawlings marry in their late twenties
and raise four children. When the youngest child goes off to school,
Susan, who quit her job to mother, does not experience the sense of
freedom that she expected. She feels simultaneously as if she has
nothing to do worth doing and never has a spare moment to herself.
Her day is taken up in waiting for the children to come home, consulting
with the maid or worrying about dinner. She becomes anxious and distant,
pulling away from her husband, who begins to have affairs.
Finally, in order to get some time alone, she rents a hotel room every
afternoon where she just sits and thinks. Her husband assumes she is having
an affair and tracks her down. Knowing that his rational world will not
recognize her "irrational" feelings she tells him that she is indeed
having an affair. The next day, she returns to the room and kills herself.

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When I finished this short story, I wondered what are the facts making
two different people linking together? Is it love, sex, or something else?
And I also wondered what is the center of a marriage or a family?
In a marriage, who did sacrifice more, men or women? Or both man and
woman should do sacrifice in their marriage or family?
Could men or women keep themselve after getting married?

And about the freedom, when a man or a woman get married, do they still
have freedom to do their own things, or the freedom just belongs to
the single people? If not, what is freedom?