Firstly sorry to hear about your grandfather, I lost my right leg below the knee, from a personal point of view I was quite non plus about it , however this is definitely an individual thing . I will say that losing my leg has made me more determined to get my blood sugars in check , losing a toe can be individually traumatic but it won’t stop your granddad doing anything , a neighbour of mine has recently had his big toe removed , he’s walking fine after about 2 weeks , there is a myth that if you lose a big toe it affects your balance, not true in my experience . the best thing you can do is be there for him for help and support as that definitely helps from a confidence point of view and that at the end of the day is the best thing to aid any depression that might exist .