Severus had never stopped loving Lily. From the moment he met her, he loved her, there was no doubt about it. He blamed himself for her death feeling he could have prevented it if he made different choices. These reasons are why he visited her grave every year, it couldn't be helped. He could not stop loving her.
Walking into Godric's Hollow, he placed a lily flower on her resting place and glanced over the note he wrote just for her.
Dear Lily,
I would have sent this letter to you. I wanted to. I shouldn't have treated you the way I did when we were in school. You were my first friend and I could never wait to see the smile on your face whenever we met. You gave me comfort when my parents' fighting drove me mad; you listened to me when no one else would.
You were also the only woman I ever loved. Things could have been different for you and me. They should have been different. The only thing I will ever regret in this life is that moment when I insulted you. I did not mean it, I never did. Had I not done that, you wouldn't have married that Potter boy and you could've loved me instead. I miss you Lily.
-Severus
Setting the note down on her grave, Severus took a deep breath and looked around. He thought of her smile and the laugh that would always accompany it. Memories of a younger Severus and a living Lily beneath their tree hiding from the summer sun flocked to his mind. These bittersweet thoughts let him raise his wand. Muttering two words, the silver form of a doe gracefully appeared. It ran around the scene for a few brief moments then vanished, leaving Severus alone with nothing but his thoughts, a note, and the tombstone belonging to his beloved Lily Evans.
A/N: Right...so, what to do to change the letter?