Ronan doesn't know when the beggining of the end started, he doesn't even know how literally the word 'end' means to you.

On your checkup to find out why it's taking so long for you to bear children, you received a terminal diagnosis that you kept secret from him. The true reason.

What's the point? You don't want to use your illness to make him stay, that'll just make him resent you more.

Both of you are on the bed, facing away from each other when he spoke, "I'm sorry, we tried."