The phrase "keeps oneself" can be substituted with several synonyms depending on the context of the sentence. Some synonyms include "maintains," "retains," "preserves," "upholds," "conceals," and "protects." For instance, instead of saying "she keeps herself busy with work," one can say "she maintains a busy lifestyle." Similarly, instead of saying "he keeps his thoughts to himself," one can say "he conceals his thoughts." These synonyms can be used to add diversity in language and make writing more engaging. It is essential to select the right synonym that fits the sentence's context appropriately to ensure effective communication.