The way I have handled it in the recent past is that I grid search till I am so far out there that (IMO) there is no way he could have been mortally wounded. I took 4 days to grid an area of swamp one time, so when I say I am satisfied, I mean I am satisfied. Thats a big weight off my shoulders, to know (in my mind) that the deer is o.k. and I haven't wasted a life.
Before I started doing this, I would simply stop for the year. I guess you could say I punished myself. I lost two years in that manner and over the course of some 20 years of hunting. That last year I got to thinking about it (after season ended) and decided that punishing myself wasn't enough. I had to be sure that there was no waste to the best of my ability. Thats when I took the new route.
I found that once I took to grid searching till I was satisfied there was no waste, I felt much better about the whole incident and could move on with hunting. I have added 2 more wounds in those last 15 years and felt good about the outcome each time because I did my level best to finish what I had started.
I know how you feel ... Trust me on that one. I think most everyone would.