"Fail to control your anger, and you'll become a slave of it," Caen told Lucifer, advising him about keeping himself in control against the only weakness which Caen found to be too obvious.
He believed that he wasn't the only one who could guess such a thing. One day, when the time was right, Lucifer's enemies could also use this trick to make him fall for their traps. And by that time, it was going to be too late.
He believed that Lucifer was a part of their team. And after helping him today, he was certain that Lucifer was going to join their team and help them in achieving their goal.
Since he was confident that this would eventually happen and Lucifer would become their ally, Caen believed that they were not going to fight against Lucifer. With that thought in mind, he genuinely advised him about his weakness.
