How do you get over a death with someone you were EXTREMELY close to?

I don’t have much of a family. The blood relatives I have are very hurtful people and my grandpa was nothing like them. He truely was the greatest man I’ve ever known. He was a father figure to me and gave me as much love as the whole family could have given. I quit my job to take care of him for his last couple weeks. So, I was at the house when he passed. I am a usually a very cheery person and I feel depressed. I rarely cry and now I can cry at the slighest thought of him. I feel this deep whole within me and I don’t know what to do. I MISS HIM SO MUCH