First summer my oldest child isn't coming home for the summer.

My son is in his last year of college, and has rented a house so he isn't coming home this summer. I find myself really missing him even though he's in college 9 months out of the year. And I have two kids at home this summer, but I'm still feeling down and lost without him. I guess that was the last bit of apron string. I didn't think I would feel this bad, but it has hit me hard. Anybody else ever felt like this? And if so, what did you do? (besides cry cuz your baby is gone for good out of the nest)