Locking in refers to the act of securing something or someone. The opposite of this phrase would be to release, let go or abandon. You can also use antonyms like detach, loosen or unfasten, which means to undo or unclasp something. Other antonyms for locking in could include free, liberate or emancipate, indicating the act of releasing from confinement or captivity. Alternatively, to set free or loosen up would provide a sense of relief, allowing someone or something to move freely. Hence, antonyms for locking in would generally revolve around the idea of detaching or releasing, providing a mental break from confinement or control.