AN: This one is written for the prompt "bad habits," focuses on Cole, and takes place between seasons three and four. Possible warning for poor coping skills involving exercise and food? Yeah, definite warning for that. I made myself sad with this one.
Throughout his life, when bad things happened, Cole knew where to turn for comfort. He would throw himself into exercising. In working out, he got a mood boost from the adrenaline. Furthermore, working out distracted him enough that he could push down on and ignore his negative emotions about whatever situation he was in. Maybe it wasn't the healthiest coping mechanism, at least in the "repressing emotions" part, but it worked well enough for him that he didn't see a need to change it. It got him through failing the Triple Tiger Sashay, it got him through the countless times his father tried to improve his dancing skills and made that disappointed face when it didn't work, it even mostly got him through the loss of his mother, although that one still hurt at inconvenient moments. Exercise kept Cole going.
So when the Digital Overlord was defeated at far too high a cost, Cole turned to exercising. He lifted weights, he climbed mountains, he went for long runs.
But it didn't help. None of it could help.
Zane was missing. Zane was gone. Zane was dead. Zane, one of his best friends, one of his brothers, part of his family, had exploded and all they had found to bury was half of his face. It was too much to bear, too much to push away, too much to work through. That much was evident to Cole, and it seemed to be evident to his remaining brothers (and how much that hurt to think, that he didn't have all of them anymore) as well.
Kai started fighting in underground rings. Jay signed a contract for a TV show. Lloyd tried to keep it together, tried to keep them all together, but it was obvious the kid was hurting and didn't know what to do. The same was true for Nya, who kept patrolling as Samurai X and kept trying to talk to them, but if the tension between Jay and Cole hadn't already been high, the fact that they'd lost their brother in battle elevated it to new extremes. Sensei Wu lectured them about the importance of remaining a team when things got rough, but even his wisest words didn't help.
Slowly but surely, they drifted apart. Kai moved out with the money he'd won from fighting, and Jay did the same with the advance from his TV show. Lloyd and Nya begged them to stay, but they were all in too much pain to make things work.
As for Cole, exercise alone didn't do it anymore, but he'd stumbled across something that, in combination with working out, could at least distract him. One day after working out for hours, he took a jog through Ninjago City and his attention was grabbed by a smell, the smell of good food, the kind that Zane would make. Used to make. Cole followed his nose to a buffet and got in line. The never-ending supply of food kept his mind and his hands occupied for the rest of the day, and he kept eating until closing time.
And that was that. Between exercising and eating, Cole filled his days, spending less and less time with Lloyd and Nya. Eventually, he moved out as well, finding a job that offered a place to stay. That it was a lumberjack position that involved lots of hard physical work and fed him well made it all the better. He knew he should've stayed, should've tried to keep everyone together, should've found ways to help them all heal, but he couldn't do it. He just couldn't do it.
What he could do, it seemed, was find his comfort from food and physical training instead of his family. Maybe it wasn't the greatest habit to be in, but it worked. It kind of worked. It sort of worked. It worked enough to keep him from thinking about Zane, and that was all he needed.