Does not being married or in a relationship after your 30's mean you fail at life?

I've seen woman who are older then 30 not complaining and enjoying life without thinking too much about relationships but with men it's different.
They won't throw a fit about it but every time some of their close friends get into a relationship, some become a bit bitter.
Why does that happen?
Does not being married or in a relationship after your 30's mean you fail at life?
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