different between yourself and yourselves ?
Singular / plural.

Mark, please serve yourself before the potatoes get cold.
Janice, Georgia, Alice, please serve yourselves before the potatoes get cold.
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Yourself is used only for a single person whereas yourselves is used for many people i.e. the people who are with the person(including the person) whom the speaker is reffering
Yourself can be preferred to use where there is singular means when someone is talking to a particular person. And in similar way yourselves can be used in plural to denote more people at a time
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Do you know the World we are living is deteriorating: the air, the water, and the land. Don't forget we brought this darkness upon us. And henceforth read again, ask yourselves what are you are going do about it?