Luke didn't try to listen in on the conversation, in part because he was trying to be respectful of their privacy and in part because the Lasat named Zeb kind of intimidated him. Okay entirely because the Lasat intimidated him. The whole time Hera and Kanan were out of the room, all Zeb did was glare at him.
When they finally did come back, Hera was looking quite smug and Kanan was looking both irritated and annoyed, but something had changed about him. Kanan stopped in front of Luke and said "Alright I will help you, but the moment we find someone more qualified, I am leaving. Got it?" Relief washed over Luke and he said, "Got it. Thank you Kanan."
Kanan turned away with a sad look on his face as he quietly said, "Don't thank me yet." Luke didn't catch, but Hera did and all she could do was selfishly hope that Luke would help Kanan just as much, if not more, then how Kanan helped Luke. "I just need to go let my R2 unit know that I'm okay, otherwise the cavalry will be beating down your door. I'll be back shortly." Luke said as he headed towards the Ghost's exit.
Once he was gone, Zeb turned to Hera and Kanan and said, "We're not really going to help this guy are we?" "Yes Zeb we are. Though if you want to know why, ask Hera." "Oh you know very well why Kanan, so don't even act like you don't." Hera retorted, "You both need each other, he needs a Master and you need someone to help you get over what happened with Ezra, it wasn't your fault."
"Yes it was Hera." Kanan said with agony in his voice. "Ezra is his own person, Kanan. You couldn't stop him from making his own choices anymore then I could stop Sabine from making hers. That's what life is, and sometimes people make the wrong ones. That doesn't mean that those in their lives are at fault." "But I was at fault Hera! I should have seen it coming, I should have protected him. He should never had had to make that choice."
Hera sighed and said "Kanan carrying around that kind of guilt isn't good for anyone. Someday I hope you learn that it's okay to move on from a mistake, rather than agonize over it for the rest of your life." Having said that, Hera left the room. Zeb, wishing he was anywhere else but in that room, stayed silent while Kanan took deep, calming breaths.
After a moment, Kanan turned to Zeb and asked quietly, "What's your opinion Zeb? Do you think I hold onto my mistakes and guilt too much?" Zeb contemplated his answer carefully, then slowly said, "What I think and what Hera thinks doesn't matter. What would your master have said about it? Is it the Jedi way?" Than he too got up and walked out of the room, leaving Kanan with his thoughts.