The phrase "falling on one's knees" often implies a sense of submission or supplication. Antonyms for this phrase might convey a sense of strength or agency, such as standing tall, remaining upright, or holding one's ground. Other antonyms might emphasize a lack of emotional intensity or urgency, such as sitting calmly or stoically or remaining indifferent or disengaged. Depending on the context, alternative phrases might include "standing firm," "refusing to yield," or "maintaining one's composure." Ultimately, the choice of antonym will depend on the tone and context of the original phrase, as well as the desired emphasis and message of the speaker or writer.