system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars] What was Darth Vader's motivation to stick with the dark side?

[Spoilers Ahead] 

I'm super new to the Star Wars Franchise. I just saw the first 6 movies this week. My question is, I know Vader was motivated to join the dark side in order to save his wife. After she died, and he was told that he had killed her in a fit of rage, I would've imagined he would see no point in sticking with the dark side.   

Padme was the sole reason he joined them in the first place - in the hopes of preventing her death. If he finds out he got her killed cause of his fascination with the dark side, why on earth would he stick by it? Wouldn't he rebel? Wouldn't he be furious at the dark side cause it got his wife killed and brought about this mess in the first place? 

I just fail to see his motivation here. What the hell was he doing for 20 years when Luke and Leila were growing up? Just being a slave to the empire and doing generic evil shit just because? Did he start thinking like a robot when he started looking like one? To me, Vader didn't seem to have a personality until he protected Luke at the very end.

EDIT: Just added a few more thoughts after reading your responses. Thanks for the answers folks!
gpt
He's basically in too deep by the time he realizes he's been duped. Vader helped destroy the Jedi and topple the Republic, burning any bridges he had. He's not able to challenge the Emperor directly (hence him wanting Luke to join him). Serving as the Emperor's enforcer is a better option than trying to disappear as a guy in a black life support suit.

He also pretty much destroys everything he cared about, reversing course after something like that is hard. Humans don't like admitting they're wrong, and it would be difficult for him to acknowledge the atrocities he committed were a mistake. It's easier to live telling yourself you did what you had to.