I'm sorry it took so long for me to reply. I totally forgot that I hadn't.
Thank you, I'm glad you liked it. At first I wanted him to question the potion that he was being given but then knowing their animosity for each other, he never would have taken a potion from Snape without knowing what it was.
I think for Snape, it's just a matter of trying to keep a last link, a living memory, of a time when he was happy. Especially since he is back spying.