It's short. Yeah.

Regret

Jimmy Bruno has a lot of regrets. Not having been a good enough father, and not having been what his wife needed him to be, for example. There is one regret, however, that is so deep and painful it overshadows all others: That regret's name is "Sean Cooper".
Jimmy knows it sounds chliché to say that if he'd known before how everything would turn out, he would have done things differently. But that's the way it is, that is the honest-to-god truth. He believes not having gone with Coop when Sean asked him to - even begged him to, really - was the biggest mistake of his life.
No, he knows it was.
Because if he'd only gone with Cooper, all of this might not have happened. He might have been able to help. To prevent this - prevent Coop's death. He doesn't know how - but he knows that Cooper would have had a chance, they would have had a chance. Somehow.

If only Jimmy had gone with him, Coop might have lived.

Instead he'd let Coop go on his own.
He'd been too scared. They would have known - they would have known - what Cooper and Jimmy were to each other. He'd had a wife, and children. He wasn't queer. He couldn't let that happen.
Excuses.
But it doesn't matter anymore, does it?

Because that one person, that one person Jimmy Bruno loves more than anything, has long since been dead.

And it's Jimmy's fault.

And that is his biggest regret.