So many experiences in life are bittersweet. I think letting go of your children can be described as bittersweet. But they can't stay little forever. They have to grow up. When they do grow up, you have to let them go. You're happy that they can stand on own two feet but your are sad because those "precious moments" when they were little are now "precious memories". You are happy and sad at the same time. Happy because they grew up. Sad because Peter Pan is not real.
I think it is called "Empty Nest Syndrome". As the children are growing up we become accustom to them being little and needy. When they grow up we are so proud and happy for them. However, that causes a contradiction in our own emotions. We want to be happy for them. At the same time we wish they were little and needy again. Don't worry though it is not a ending only a beginning. They do not need us in the way we are used to but the new book has begun.
They now need you in different ways. So don't be sad. It's not an ending only a beginning of a new chapter. This took me a while to learn also. I was probably one of the most clingy and needy parents of all. It broke my heart but made me grow also. This lesson is more about change and growing rather than an ending. So it will help to remember that new things are coming your way. New ways to be needed by your child, sibling etc are about to change who you are and what you are used to. Do not be sad about an ending. Be excited for a new beginning.
Absolutely, I thought it would continue to hurt. However, she made me more proud than I could ever be sad. She still makes me so proud. She is one of the best mothers I have ever met. She has morals and respect. I couldn't be more proud. So don't feel sad for long. You are allowed to grieve of course. But in the end, the leaving of the nest is only the beginning.