First, concerns about physical changes. As you said, no matter what the physical condition is when you are young, the elderly will have some diseases. Most of them will feel worried and scared about their health. This is a normal mental state, please don't care. Especially for an old man like your grandfather who was in good health when he was young, this reaction will be more prominent and easier to understand, because he has never had much physical discomfort before.
Second, the awareness of the passage of time. Facing the coming end of life, the elderly will be more sensitive to time.
Third, I am worried about the pain and tension caused by death. Fourth, I am worried about the intellectual and emotional reaction caused by death. These are normal psychological changes of the elderly.
Of course, if these are not enough to relax you, the following stages of psychological change that are common to the elderly may help you.
1 Deny that the elderly have isolated themselves from their surroundings. Family and friends must fully understand this stage and it is necessary to go through it with the elderly.
Angry old people generally show anger, full of anger, and it is difficult to restrain. In order to transition to a calm and tolerant state, this irritable stage must be overcome.
3 Trading the elderly are particularly easy-going to others at this stage, and people around them can make important help to the elderly at this stage.
4 depressed old people face everything that is doomed to lose, depression, sigh and pessimism. In this state, the old man cut himself off from the outside world. At this time, people close to the old man should consider facing death and accepting the fate of the old man in order to restore inner peace and serenity.
Accept your fate, death is coming.