Lucifer stood next to the pond watching Sam walk away. He shouts after him but Sam doesn't turn around. He just keeps walking away. Lucifer is crying, really crying. More than he has cried ever. He has had such a shit few weeks. He lost his mother and his best friend. He still has the taste of the beer Sam was drinking on his lips. He doesn't like that he has broken his own heart and possibly his best friend's heart too.
Sam walks away, ignoring the shouts from Lucifer. He can't forgive Lucifer for what he has done. Really, how do you forgive your best friend after they kiss you and tell you they are leaving? Sam doesn't know. He doesn't go straight home. He passes Lucifer's apartment. There is a 'To Let' sign up. He cries even harder. Next he goes to Dean's apartment. He knocks on the door and it is answered by a very tired looking Castiel.
He asks Sam what is wrong and Sam explains what happened that night. He asks where his brother is but Dean is still sleeping. It is nearing two o'clock in the morning though, so it isn't surprising. Castiel lets Sam sleep on the couch that night, and Sam is grateful. He really was heartbroken when Lucifer revealed that he was leaving.
Lucifer woke up a mess the following morning. He had packed his stuff days before and now he was leaving. He picked up his phone and typed Sam's number in. It rang twice then went to voice mail. He left a message saying how sorry he was and that he didn't want to leave but his brothers needed him. He picked up his car keys and left the apartment. He posted the apartment keys into his landlords postbox and he walks out to his car. Lucifer slings his bags in the bag seat and walks around to the drivers side. He drives to Sam's apartment and gets out. He knocks on the door but there is no answer. Lucifer pulls out a letter from his coat pocket that he wrote for Sam and puts it in the mail box. He gets in to his car and commences the long journey back home to his family house. He feels like whatever song he listens to is a sad song because he can pick out memories of Sam in them all. His eyes cloud up with tears and he tries to rub them away, only to release more tears.
Sam walked back to his apartment. He passed Lucifer's on the way there and he saw no life through the window, also, his car wasn't there. Lucifer had left. Sam ran the rest of the way, hoping to beat the inevitable tidal wave of tears. He pushed the door open and saw a letter written in Lucifer's neat script. He picked it up and carefully opened it. The letter said how sorry Lucifer was and that he would really miss Sam. He ripped up the letter in upset and left the pieces scattered all over the floor of his hall.
Sam went to the kitchen to make himself a cup of tea. He was sobbing. He took the tea to his front room and snuggled up in front of the TV watching daytime TV. He sat there for hours. He didn't know what time it was. He didn't know what the date was. He was hungry but didn't have the energy to stand up and go to the kitchen. And above all else he really missed Lucifer.
The next few weeks were really hard for Sam and Lucifer alike. Sam had to get used to living without Lucifer in his life. Lucifer had to learn to live in a different state without Sam.
Lucifer had got a job as a PA for a lawyer. He hate the job. More often than not he made a half assed attempt at the simple tasks his boss asked of him. As much as he hated working for Roman Enterprises in the call centre that job was so much more rewarding than this one. If Lucifer hadn't taken that job he would never have met Sam and he wouldn't have made a best friend. Also, what made him feel even more guilty, he wouldn't have ever needed to leave Sam.
Sam was still working at the call centre. Someone new had taken Lucifer's place and he had been making a sort of effort at trying to befriend him. Apparently it worked, he was going out for a beer with Gabriel at the weekend. Everyday after work that week Sam went out for coffee with Gabriel. He felt that he had made a successful attempt at trying to fill the hole left by Lucifer. It worked for the first few days of knowing Gabriel but it stopped working. Gabriel reminded him of Lucifer. A more sarcastic version of Lucifer, but still a version of Lucifer.