When you have time, you can spend more time with your parents, and if you can't find the time, you can often talk to them on the phone or video chat, so you don't let them think that you've forgotten them after you've got your own life.
People who are older are afraid of being alone, afraid of being forgotten, and in need of security and a sense of being, just like children. My parents are not too old though, in their middle age. They also feel lonely when both my sister and I are not with them. Mom always tells me on WeChat that she misses my sister and I. She says that there is very little talk in the house since we left, and that she and dad are always busy with their own things, and don't have much to talk about when they get home. Dad often joked with my sister, why don't you just not go to school, stay home with me, and then invest in a small business for you, not far from home, you can often come home to see me. I know they miss me and my sister, parents are like that, all the time want to see their own children, the child always snuggle them around the child. As a result, I talk to them whenever I can, talk about the parents, what they ate, what they did, and tell them all the fine things I can.
My grandparents are even more afraid of loneliness, they have all retired, the most important thing every day in addition to three meals a day is to wait for our news. I remember there was a period of time I was very busy, too busy to care about eating, as soon as I had time to rest, I would seize the time to supplement sleep, many days did not have the opportunity to chat with grandparents. My grandparents couldn't resist calling me, and I told them I was so busy that I forgot to talk on the phone. They have been comforting me that it is okay, they are not in a hurry, it is a few days without a phone call some worry, the end of the hanging up the phone is still a say, let me have time to call them, they do not want to call me, because I do not know when I will have time, for fear of disturbing me.
We will be old one day, and there will be times when we are afraid of being alone. If you can't be with them often, at least let them know that we haven't forgotten them and we are always there for them.