How do i get over the loss of my 20 year old cat?

My family and I recently had to put our family cat that was 20 years old down. He had a bad mouth infection that caused him to have a large bump in his mouth and he couldn’t eat properly. He was like my best friend. I saw him everyday all the time. Now it feels like what ever I do remind me of him. At the times when I felt like I had no one I could always go to him to make me laugh or be happy. When my grandpa passed away My mother (his daughter) was looking through old photos of my grandpa and my mom and she was in tear. Our cat climbed up on the bed and cuddled with her. He was the best cat i could have every asked for. I miss him so much. I know that i had him in my life for a reason. I just wish I didn’t have to feel so sad and cry all the time. I know that he’s out of his misery, I just feel like I’m alone now.