The antonyms for the word "casting away" would be "keeping" or "holding on". To keep or hold on to something means to retain it, to not let it go, or to prevent it from being cast away. For instance, you might keep a cherished possession, such as a family heirloom or a sentimental gift, because it holds special meaning to you. Alternatively, you might hold on to a relationship, a job, or a dream, because it represents a goal that you are actively working towards or a person that you want to keep in your life. Thus, while casting away signifies letting go, keeping or holding on connotes the opposite: perseverance, commitment, and attachment.