Grief. Aging represents losses of every kind. Older family dies and you become the matriarch (or patriarch), children grow up and move away, so often that leads to downsizing and giving up assets in the process. Then there's loss of friends, independence, youth (and all that represents), potential loss of physical or cognitive functioning, lessening of time or ability to do all you still want to do, decrease in social opportunities and family time. There's retirement, so loss of career, loss of a place in society, maybe loss of identity and work connections and all the rest of the loss retirement brings. Aging is a breeding ground for depression, loneliness, change, and existential considerations. It's a tough time.
So if you're in the grocery lineup and the senior in front of you is taking too much time chatting with the cashier or bank teller, your ageing parent calls you too often, or you feel put out because your grandma is taking too long at the doctor's office or is hesitant to get out of the car when you drop her off, be gracious - it could be their only source of joy or connection that day. Be patient when you have to walk behind them, offer to reach an item from the top shelf, find something to connect with them about, offer a compliment or just wish them a happy day.