Brief little pep talk for the New Parents... You may be feeling very bothered right now: the nest isn't empty, it's haunted! You're doing good and then intrusive thoughts: they're away! [Remember, they're learning to fly].
The good news is there is a flip side to this. There will be a time not far off that your reptile brain will flip to "they'll be heading back to the nest soon." And you're are going to have superjoyous instrusive thoughts. You will be in a great mood for no conscious reason. When you think about why, you will feel happier than you can remember. You will literally jump up and down spontaneously. It's really the BEST feeling, and it doesn't have this pride/pining duality when they're away. It's just joy, joy, joy.
And while the pangs and pinings of separation, I assure you, diminish, the anticipatory joy of them coming home does not seem to diminish at all. It grows.
So when you're thinking "man, I am SO sad right now", know that you have a whole LOT of "I cannot remember being this excited about anything, ever" ahead of you.
You will be awed how simple eye contact with your child will transform your universe. So consistently that the anticipation of it will buoy you weeks in advance.
The (little) grief diminishes, the joy grows.
Take it day by day. They got this. You got this.