Yes, you will miss the kids when they move out, but you will adjust to your new freedom. And odds are they will come back often, seeking your advice and for companionship.
However, you must insist the kids move out at a certain point or you will harm them, perhaps irreparably. They can’t truly grow up until they are on their own.
You bounce better when you are young. Struggle is a natural part of growing up, moving out and finding your way in the world. There will be scars. That is the natural order of things.
It hurts. Life hurts! You fought through the difficulties when you were young. It is how you got where you are. A bird never learns to fly sitting around in the nest.