If you didn't already know, I'm a big fan of Star Wars and Star Trek, and find myself thinking about
All my life I've idealized the Vulcan (Star Trek) and Jedi (Star Wars) way of thinking, logic before emotion, etc., but you know, that's only (no offense to fans) viable within the somewhat narrow plot structures of the story. You try that in real life and see where it gets you.
Be that as it may, Obi-Wan Kenobi (in both OT and PT) seems to have the Jedi Code down pat. He doesn't show any emotion, he's just this cool, calm and collected dude who does what needs to be done. He shows a little bit of passion once in a while (like when he fights Grievous) but it's kept in check.
Then you have Anakin Skywalker. He's always been emotional, from TPM, through AOTC, and into ROTS. So Anakin turned to the Dark Side, despite his Jedi training, and yet through these movies we see over a dozen Jedi (on the council, fighting alongside Mace Windu in AOTC, Order 66 scenes in ROTS, etc.), these guys of various races for whom the training was also successful.
So we are led to believe that Anakin is the odd man out here, the "one" that turned to the Dark Side. But looking at it, I think Anakin was the most human of them all. (Maybe humans make bad Jedi, hence why most of them on the council are not human?) He was angry at the slave traders for what they did to his mother. He was angry at the Sand People for killing his mother. He fell in love with a beautiful girl who took a special interest in him.
And, while the Jedi Order forbids him to love, a Sith offers to protect his unborn child(ren) from a perceived threat (albeit probably created by said Sith and somehow sent to Anakin's dreams), he changes sides. Not to mention that he feels underutilized by the Jedi Council. Within the SW universe we see that as a bad thing, but in real life, if you work for one company and they're not paying you what you feel you deserve, they're not utilizing the specific skills that you bring to the table, and their competitor offers you a position that satisfies both pay and skill, moving is the wise choice.
Back to my first paragraph, about trying to be like the Jedi in real life. No, I've never dressed up, I don't own a lightsaber replica, and no, I haven't tried to live my life as a Jedi (or Vulcan). The way of life does appeal to me, however. Thinking about it, beyond the confines of the story, a Jedi must be a real coldhearted son of a bitch, right? While I agree with why the Jedi (and Vulcans) suppress emotion, one must not forget that the most powerful emotion isn't hate, it is love. I mean, you can kill for hate, and you can kill for love, but can you kill yourself for hate? Not as readily as you would (e.g. take a bullet for someone) for true love.
And I don't just mean love of a spouse, a partner. I think it's the Jews, the Hebrew language has six or seven words that translate, in English, to love. Love for a deity, love for your spouse/partner, love for your offspring, love for your parents, love for your siblings, love for your friends, love for the self. Without researching it, I think those are the seven types. Then there's patriotism (in SW: love for the Jedi Order, and/or for the Republic), a kind of love as well, more a passion for something. I know the Jedi know loyalty, but how passionate are they, without using emotion?
Human nature is such that, if you forbid something, the mind, or people in general, want it more. Alcohol and a certain herb classified as a drug were/are many times more popular in their respective prohibitions. You tell a kid not to touch something, they're going to do it anyway, to see what happens, and to see what you're going to do about it. Put that into the SW universe, and you take a kid (doesn't matter which one, but Anakin for example) who is Force sensitive, and offer to train them, repress their emotions, it's going to come out sooner or later when human nature takes over. Maybe whatever race Yoda is (Wikipedia gives it as Whil, but more official sources have his race unnamed and say he ISN'T a Whil...) either don't feel emotions, or like Star Trek's Vulcans, they've phased them out over a few centuries, but humans in SW are enough like humans on Earth; that's why Star Wars appeals to us. We can see ourselves in Luke or Han or Anakin, they're like us. And thus prey to the same human nature.
I thus conclude that, by nature, Jedi are prone to turn to the Dark Side by fault of human nature.
I posted this over on GameFAQs with a couple minor changes, for example one word had to be starred out due to a bad-word policy, and the last paragraph had to be put in the first reply, along with notes as to why it was split (a technical limitation in the GameFAQs forum system that limits post input to 4,096 characters). And also, as a final note, if you aren't as familiar with the Star Wars universe or more of a casual fan, you can click some of these links above to be taken to the Wikipedia page on that subject.