He's still trying to rationalize what he did. It's been years; in fact, a long time ago. He's an old man. History has forgotten him. No one remembers him at all, in fact. Even Lando, whom he tried to get a helping hand from not long after the signal event played out, turned him away. "Not my problem," his old friend had said.
He lost everything because of it, just when it seemed like he had finally turned the corner, erased all his problems, earned a comfortable and lasting retirement. "It's not my fault," he used to say, to anyone, everyone. No one listened. No one believed him.
In another lifetime, one he abandoned, one that never happened, when he showed up in the Falcon, he gave Luke all the clearance he needed to take the shot and destroy the Death Star, just in the nick of time. They'd parted with the belief that he was certainly not going to return, that he was turning his back on the whole business. But even before leaving he'd had second thoughts.
The thing is, it seemed like a good idea at the time. And the other thing is, he realizes now that he was just being greedy. That was the single thought that had come to possess him, all because of a stray transmission he picked up, an Imperial conversation he realized as taking place between Darth Vader and the Emperor. One said to the other, Luke is more important than he seems; he's valuable in two ways: as a target that will need to be eliminated, or failing that a useful new recruit.
If he'd never intercepted the transmission...
But he can't think like that. He did, and his first and only thought was that he could do it. He could eliminate this threat. He didn't care, at the time, about anyone or anything else but himself. He certainly didn't take seriously any of that talk about the Force, which as far as he'd been concerned was just some hokey religion that belonged in the past.
In hindsight, when Luke's sister was asked to fulfill the role intended for him, and he realized who Luke's sister was, and another version of a life that would forever be denied him, a lover who would forever hate him...
He'd made a transmission of his own almost immediately. He laid out his plan, why it was fool-proof, and demanded payment upfront. It was granted without question.
So he turned his ship around and headed back to the Death Star, and at the last possible moment was there to watch as Luke prepared to take his shot. He took his shot, directly at Luke, who was gone in an instant.
And just like that, he became persona non grata. He did receive his payment, but that was it. The Empire denied any relationship with him. The Rebellion considered him an enemy. Thanks to Jabba, the Hutts cut him off from everything he had ever known, even with the debt settled. One way or another, he had acquired a very bad name. No amount of wealth could change that.
The Empire lingered for a few years, and then finally collapsed on itself, died of its own accord. The leaders of the Rebellion assumed control. Luke's sister led a whole renaissance. And suddenly he had nothing.
Now he wonders, is he delusional to think it could have played out differently? Even if he hadn't...He tries not to think about it, he really does. But it's very hard. He'll always be known as the man who shot first.