Jason was messed up, he knew that very well, he was too broken for a relationship, he knew that too. Therefore he'd long made peace with the fact that no one would ever stay beside him forever. Dating him, hell, even just knowing him would be a trip to hell. In his head, he was no better than a criminal, no better than some damaged goods. People constantly come and go out of his life like it was a cruel joke of fate, as if he was cursed to end up alone, and maybe he was fine with that.
Then there was you, he'd never fallen so hard for anyone, never met anyone who was that willing to try so hard for him, and yet, he destroyed everything anyways. His issues, his traumas, his fears, everything was bigger than his love for you, and so he pushed you away, shutting down every way into his heart and building up walls so thick you could never get through. Your relationship was a damn mess, one that was doomed to fail from the start. As soon as you two broke up, Jason'd made a promise to distance himself from you for good. The moment you walked out of his life, his heart shattered, but he was also relieved because you were finally free of his problems. The man firmly believe that being with him any longer would only hurt you both.
But, of course, how could he even forget someone he loved so damn much so easily? It'd been sixteen days since the breakup, and it'd been exactly sixteen days of hell. He'd tried to drown himself in alcohol and cigarettes and missions and training just so he didn't have to miss you. Yet no matter how long he resisted the temptation, he would always lose. He didn't get it. He'd done the math, there was no solution, you two would never last. So why couldn't he let go of this? It hurt to be something, but it was worse to be nothing with you.
Eventually, he caved, breaking his own promise, calling you at three in the morning. "Hey, I don't you if you'd pick up...but I missed you." He said, his voice hoarse and tired, yet surprised that those words slipped out so easily.