If he was the one in your shoes, he knows without a doubt that you would do the same for him. Even if he feels he'd never deserve your kindness and empathy.  
For every second since the day of your accident, he's spent it taking care of you, being there for you, repeatedly answering every one of your question's that you forget when you fall asleep...as if your slumber is a hand, wiping clean of a slate, leaving behind a blank canvas for you to refill upon waking the next day. 
You both have experienced good days, and...the worst days of both your lives. All of which you forget, though he never would. 
There have been days where you've woken up and come downstairs and screamed when you saw him in your living room, asking in a panicked voice who he is, why he's here, and while he would try to calm you down, you would throw things at him. Things like books, pillows, once a cup, out of fear that he was an intruder here to hurt you. 
When in reality...he was your HUSBAND, who was here because he loves you, because he wants to be there for you. It was those type of days that really...broke him.
As foolish as he may be, he hoped that one day, you would come down those stairs and smile at him and tell him that you love him. Like you used to...though as the year went by, Alastor remained the same, all the while you seemed to drift further and further away. All the while, he was forced to stand by and watch, unable to fix you.
What a cruel twist of fate. If it is true that Y/N was a hand in Alastor's karma--some sick force using an innocent soul that Alastor fell deeply in love with, changing her completely, making her lose a piece of herself--it made Alastor think that he was a curse to you. 
But as selfish as he is, he wouldn't change it. The one thing he WOULD change was never going on that walk the day you hit your head. Everything else...no matter how many chances he had to change it; he would demand it remain the same. 
Maybe...just maybe, by choosing each and every day to stay with you--no matter how painful or hard it may be--it would help redeem a piece of him that he feels is guilty of the cause to your accident.
But...that is a simple maybe, and nothing more. 
Upon being the first to wake up in a separate bedroom down the hall, Alastor gets up and gets dressed, styling his hair and adjusting his monocle, before going downstairs to make the morning coffee, and read the morning newspaper in the living room--as he always does in the morning, hoping that with this every day morning routine would perhaps one day stick in your mind, though it wasn't likely.
Alastor sits down on the longue chair, crossing his legs and beginning to read. The grandfather clock ticks and tocks in the corner, almost in a haunting manner, causing Alastor to glance at it, his brow raising. 
7:30 already? Strange...you usually come down at 7:10. What caused you to be late? Instinct wants Alastor to go and check on you, to make sure you're okay, though he refrains from taking such an action, in fear that by entering your room, you would have one of your panic attacks from his sudden appearance. 
Wanting to avoid making you uncomfortable at all costs, he even took down all the framed photos of you and him that used to hang with pride on the walls. Every wedding photo, every memory book you would always make when the two of you were dating...he stuffed them all away in his closest. Memories you aren't able to reach and find in your mind...and memories he doesn't want to be reminded of.