The “Empty Nest” hits some harder than others. You will eventually find it less worrisome, and probably liberating.
Your young ‘un needs to Be Free. This is their time. This is what you raised them for, with good values and examples.
Trust in yourself and your child, and sleep well.
When we took my daughter off to college, back in the nineties, I didn't feel particularly emotional about it ... until we got to the campus. Walking around there, I was overcome by a wave of nostalgia. This was college! And college meant me! Where did I fit into this picture? I didn't! It was emotionally very confusing.
This may seem to be a very selfish perspective, and I can't deny it, but it's all about the same thing ... change. "Turn and face the strange changes ..." in the words of the poet.