I agree - I think he would've seen Lily smiling at him, letting him know that he was forgiven. It's losing her friendship that devasted him, then when she died ... it broke him.
Will: I'm in love with you. Will you marry me? No matter what you say, I'm going to be in love with you for the rest of my life...you own me. No matter what you say ....
Mac: Yes. I'm saying yes.
Will & Mac (The Newsroom)