I know that this can be a really difficult day/week/month. Sometimes it is made sad by your son/daughter’s excitement. It is always ridden with anxiety.
Today your relationship changes. You are still their parent. You always will be. You don’t have to worry about “losing” them. And don’t let the fear of losing them cause you to not let them grow up. They are ready to not have curfew, ask permission to stay up until 2 AM, or tell you whether they did their homework. They NEED to make decisions about majors, classes, and roommate choices on their own. If you give them enough freedom on these decisions then they may even take joy in asking your opinion. And they may even learn to do that for big decisions for their entire life.