Resignation of work partner

My OIC is resigning after 8 years. I’m starting to feel emotional about this. I want to hug him more often until the day he leaves. The trust and work relationship that we have cannot be replaced easily. He is imperfect but he’s been loyal ever since to our company. He’s finally pushing thru with his resignation to grow and try other jobs. Why does this feel like a romantic breakup? Damn. Didn’t expect to be this emotional. It got to a point where he knows how I make decisions. He knows the directions that I will take. This is hard.