The phrase "casts away" implies discarding or getting rid of something or someone. The antonyms for this phrase would be "keep," "retain," "hold onto," "approve," "accept," and "embrace." Keeping something means that you hold onto it, value it, and take care of it. Retaining something implies the process of keeping something for further use or reference. Approving something means that you agree with it and support it. Accepting something means embracing or acknowledging it, while embracing something implies accepting and welcoming it. Overall, these antonyms provide a different perspective to the idea of holding onto something, which contrasts highly with the notion of casting away.