Luke skywalker has so much rage inside him and I want people to recognize that. No he's not a shy baby boy, you know how much grit it takes to keep on doing and remain optimistic at the face of insurmountable evil? That boy is full of emotions. And yet he is kind. That's the key to his character - that he is full of rage but he doesn't let that stop him from hoping.
He definitely has a hair trigger temper - hell, his main character flaw in empire strikes back was his impulsiveness and recklessness - and he's so much like vader, he wants and loves so strongly and he despairs as strongly too. And what does he do with that temper? He fails, he loses, and he blows up and wrecks shit, but also that temper is the flip side of loving, and he embraces that too, he loves with all his heart. Point is, he's a very action and emotion oriented person, and that's what pushes him so close to the dark side; he's fatalistic, he's sometimes ridden with guilt, he's emotional.
But then he learns patience, he learns gentleness - learns to be a jedi. It's all learned; do or do not, yoda says, and he learns to do, to keep hoping. He isn't born as a sunshine boy, it's not his nature that makes him that way - he's naturally emotional, kinda whiny, full of rage; all the hallmarks of a darksider, but he learns to grow beyond that. That's how he can extend such an understanding hand towards sith and dark siders, his father - he knows the dark side. He understands it, he flirts with it, and yet he chooses to do better.
The meaning of luke skywalker in the star wars narrative is hope - hope isn't a magical deus ex machina that solves all your problems. It's not there all the time from the very start. It's something you cultivate, just like luke did throughout the trilogy.
Hope is continued existence. It's optimism that perseveres. You know that line of bravery being doing it in spite of the fear? Well, hope isn't the absence of giving up. Sometimes it's just screaming crying trying to kill your own father, but it's also making the right choice and trusting vader to make the right choice, too. If there's one good thing about the sequel trilogy, it's that - luke may have run away, he might have done some... uncharacteristic things, but that doesn't mean he's lost hope. He returned to fight again after all, didn't he?
Even if you fuck up, you return and fight - with a relentless optimism that being good will be enough, that the world is a better place for this choice. And Luke does that, again and again - still carrying all those emotions within him. He's a fire that burns strong and bright; he's sunshine and tempered death.