[We can either attribute it to wishful thinking, or "Sebastian isn't always all that smart about things".]
Of that, I am well aware. [Sebastian would love for Ciel to let go of his painful memories and move on, of course, but alas...]
Yet as it happens, the young master has chosen to accept his line of work, and he has no interest in recovery. I, being merely his servant, not family, follow where he leads.