Not to be crazy about the star wars legends books or anything, but there is something so important about the fact that Han Solo was succeeding in the Imperial Navy before he met Chewie. It's important because he could have made ascending through the ranks his goal. He could have kept his head down, had a good salary, and a good life. All he needed to do was turn a blind eye to the atrocities of the Empire, as so many before him had done.
But he can't do it. He can't turn a blind eye. He rescues Chewie not because he has authority problems or because Chewie can do something for him, but because slavery is wrong, and Han knows this, and he refuses to be complicit even if it ruins his own life.
And it does ruin his life! He gets blacklisted from any respectable shipping jobs! He has to turn to crime and smuggling again, even though he fought so hard to get out of it and go legit!
Even with those consequences, he still wants to refuse Chewie's Life Debt. Because he didn't do it for personal gain, he did it because of his principles, because he's a good man.
