"Keep upon" can be replaced with various synonyms depending on the context in which it is used. Some common synonyms for "keep upon" are "maintain," "sustain," "uphold," "continue," "persist," "adhere to," "abide by," and "follow through." While "keep upon" generally refers to a continuous action or behavior, synonyms like "maintain" and "sustain" focus more on the preservation or upkeep of something. "Uphold" and "adhere to" imply a commitment to a principle or standard, while "continue" and "persist" suggest ongoing action without interruption. "Abide by" and "follow through" both emphasize the importance of following a plan or agreement.