Think of 5 people who played a significant role in your life in the past but who have since moved on.
Perhaps, for whatever reason, you’re no longer friends.
Perhaps they were a colleague who moved on to work for another company.
At the time they were in your life, no doubt you took their presence for granted. And whether or not, when they left, they left a gaping hole, at one time in your life their presence was significant and positive.
Find a way of getting in touch with them, send them a card, write them a letter, drop them an email.
Find a way to get in touch and tell them how grateful you are that they were part of your life.