I'm so sorry to hear about your father's diagnosis. It's understandable you regret not being more forceful in encouraging him to quit smoking, but at the same time this was probably outside the realm of your control given his lifelong habit.

My mother was diagnosed with breast cancer a few months ago—fortunately at an early stage—so I can relate in some capacity to how devastating a serious family illness can be.

Words fall short here, but I truly hope that you, your father and family will navigate this period with as much love, affection and comfort as possible.