One of the hardest things about "growing old" is watching those around you. I am still me, and day by day I may change, but I am still me on the inside. In some ways, getting older is like the frog in the pot. Put the frog in boiling water and it will jump out. Put the frog in cold water, and turn the heat up a tiny bit at a time, and the frog will let itself be cooked. Getting old happens a degree at a time. Before you know it, you have a belly and back aches and the strong desire to color your hair blue.
But while one is continuous and contiguous with ones younger self, one notices things in the other people in one's life. Sometimes it just seeing a friend who you only see at the gym, out to dinner in fancy clothes. Sometimes its family members who live far away. These people have aged, and sometimes to a remarkable amount. The frog just jumps out of the pot.
The temporal bone is on the side of your head, and the temporalis muscle lies right above your jaw joint. They are called "temporal" not because your mind is your temple (despite what you may think). The "tempe" is from time, and the sides of your head, according to the ancients, is the canvas where Time's fingers first paint. Grey at the temples? Grey in time.
Sometimes it is not just grey beards and a shaky gait. Sometimes it starts being cognitive stuff. And if people dislike the idea that their bodies are aging, let me assure you that they like the idea of their mind aging even less. The clinical word for aging-illnesses of the mind is "dementia" de- for un- or bad, and "mentia" for mentation or mind. But as spastic, a very particular neuromuscular medical finding, was an childhood insult for kids you didn't like, demented is an insult for horror movies. And no one fancies themselves in horror movies, either as the monster or the victim.
So the first part of my advice about elder parents (or friend, or person-of-closeness-for-whom-a-standard-word-does-not-exist): acknowledge that it is hard for you. These are your (perhaps) beloved parents. Certainly these are people you remember being young and vital. They are people who (allegedly, in the best possible world, if things had maybe been different) cared for you. Who protected you. Who fed you, and now, now they are old, and weak and, yes, a bit pathetic, compared to your memory. This isn't easy. I remember, well before dementia set in for my mother, seeing my parents walking down the street. Given where we were, at my sister's last apartment, they must have been in their 60's - the age I am now. I was going back to grad school, or postdoc? I had said goodbye and saw them walking away to visit friends who lived in the same city as my sister. They looked so old! This little old couple out of a movie or a story or something. Not my parents. I remember thinking: when did they get so old? And now: why didn't I run back and tell them that I loved them?
I've loved, been friends with, still am friends with, taken care of, and more, many "old" people. Old defined as older than me. Sometimes its not hard to be a friend to someone with a bad memory, or take a meal to someone who can't cook. Yet when it gets to be family, all the emotions get in the way. Stuff from when you were 8 or 12 or 16 or 30 shows up in your head, demanding attention. You may not be able to say "out damned spot" or you may, and the spot will stay. Just acknowledging it, seeing it, may help you set it aside.
One of the hardest things I did when my Mom was in the early-ish stages of Alzheimer's disease was realizing, and giving credence to the idea that I could no longer fight with her. That all the issues and tensions were going to be moot. She, strong intelligent and very hard on me, would get furious and stop talking to me if I tried to argue with her. And sometimes she would cry. If I tried to comfort her tears, she would double down on the anger and say very hurtful things, things she knew were hurtful. What kind of things? Things like "you will never be a good scientist". Or worse. She knew where my weak places were. In the beginning people with dementia are smart, and articulate and cruel. Executive function is one of the first things to go: the part of brain and personality that keeps civilization going, that keeps people from cursing and saying the worst that they think of.
I had to let go of the past. I had to say (and say over and over): you cannot fight with her. She is not the person she was. It felt unfair. It was unfair. It felt like she won in the end. That I could never convince her of who I was? But who ever does win against their parent? By the time you can cognitively win, you are not playing and fighting with the opponent of your youth.
Eventually, I reached that place, and really, things were much easier for me. I was a duck and her words rolled off my back. Yes, Mom. Whatever you say Mom. There are other coping mechanisms. Other strategies. And, really, people who care. Let yourself cry and mourn what is lost, because truly, things are being lost. But you, you are still continuous with the glorious child that you were.