Whenever Lance or someone else is in danger, the paladins never choose to help Lance first, and Lance... well, he learns a lot.
Initially, he even tries to argue about the blatant disrespect, but there's always someone who tells him, "Really, Lance, how self-centred can you be? We had to choose between saving you and an entire planet. It's not our fault you ended up in that situation."
At a certain point, Lance internalises all of this. He realises that if anyone is expendable, it's him. So, why not use him?
If someone has to die, wouldn't it be better if it were him? This leads him to be careless about his own safety, especially if someone else is in danger, and it takes far too long for anyone to notice.
When someone finally notices, Lance has been kidnapped in the princess's place a dozen times, shielded Coran and Pidge a hundred times, and stayed behind for Shiro, Hunk, and Keith so many times he can't count. But he's still got the scars and a very protective Blue Lion.
And when the team tries to talk to him, Lance simply shrugs, "You said it: I don't have to be self-centred. There are people more important than me."
Horror doesn't begin to describe the team's reactions to hearing words they'd used so casually again, words they'd all benefited from without even realising it.
Keith will have to work VERY hard to prove to Lance that he is worthy to be saved, and that they were the ones at fault, not him. Above all, Keith will have to work hard to make up for his mistakes because he was the one who messed up the most.
("It was between you and Shiro, Lance. I will always choose Shiro first.")
