Sam died first and Dean accepted it. They couldn't cheat death forever. And Dean was tired. Tired of the hunting. Tired of the life on the road. Tired of losing everyone he cared about. He burned Sam's body and walked away. If he tried to bring Sam back, there would be trouble, there was always trouble.
That night he sat on the Impala under the stars. His favorite angel appeared by the car silently, but Dean knew he was there. Cas walked to the car, paused, looked into Dean's eyes, and placed a hand on his shoulder. Dean slumped over, dead.
And then he woke up. In the Impala, on a dark road, in heaven. He looked around, sighed, and started driving. He didn't stop at any of the memories, but he could see some out of the corner of his eye. Him and Sam at school as kids. Dean always thought his little brother was cool, even if the other kids would tease him. Dean getting Sam from college. The time they became brothers again. The last night on earth. Laughing with everyone before it all went bad. Living with Lisa and Ben. Having a normal life. And every night he had sat on the hood of his car with Sam, drinking beers, and listening to Cas's stories of heaven.
Finally, Dean saw the end of the road coming. He kept driving to it, speeding up, wanting to just find Sam. Sam wouldn't've stayed out in the memories, he would've known Dean wouldn't wait. Dean would have looked for him.
All of a sudden, he was no longer in the Impala. He was in Bobby's house, and everyone was there. Jo, Ellen, Ash, Bobby, Cas, and Sam. He hugged some of them, kissed Ellen on the cheek, got called an "idjit" by Bobby. Sam was the second to last in the line of his friends, and just hugged Dean, smiling.
"Glad you're here," he said, clapping Dean on the shoulder.
Cas was the final one for Dean to greet, and the others had gone to get plates to eat dinner, which was Dean's favorite - steak.
Dean smiled at Cas, and the angel smiled back.
"Thanks," Dean said quietly.
"You and Sam, your time is finished. The world can find new heroes."
Dean chuckled. "I wouldn't call us heroes" he started, before he was silenced by Cas's look.
"It is your time to rest," Cas said, looking around. "Be with family. Eat good food. Watch old movies."
"And you?" Dean asked. "Are you going back-"
"I am staying."
Dean broke into a full grin. "Well alright then! Let's get some food!" and he dropped his hand onto the angel's near shoulder, making Castiel smile too.