Second wind

A story about a young man who undergoes a lung transplant. Beyond just the lungs, he feels as though he has gained something more from the donor. He becomes aware of this through a series of visions, in which he is overwhelmed by anxiety about aging and the issues associated with it, primarily breathing difficulties. In the end, he comes to terms with it –⁠⁠⁠⁠⁠⁠ he takes a breath.