busy* Make sure the people who matter to you know how you feel about them. Say it in their own love language, not just yours. For some people it's words, but for others it is something else like service or time.
* When someone is moving out of your life for whatever reasons, take steps to fill the roles they serve in some other way. Maybe you used to socialize with them once a week, or they drove you to get groceries, or whatever. Both the social and the practical roles need to be filled, or there will be a huge gap when they're gone, and then that creates functional problems on top of the challenges inherent to coping with grief. Usually you will spread out the roles over different people, which helps avoid the sense of trying to "replace" the irreplaceable. This makes it more feasible to let go and reassure the person that you will be (eventually) okay.
* Treat every goodbye as if it were the last. One day it will be.
