I’m sure we’re all well aware of the story of Obi Wan from front to back, but if you really analyze everything this man has been through, you begin to realize how strong he is emotionally. 

He ends up losing his master way too soon in his arms

he is given the immense task of training the Chosen One

his love interest dies in his arms, killed by the same person who killed his master

His apprentice (and practically brother) is lost to the dark side seemingly forever (until Luke comes into the picture) 

He has to sever the limbs of his former apprentice to show him what arrogance can result in.

He has to watch Vader burn, not having the strength to kill someone he holds so dear to (which, in retrospect, is kind of counterintuitive with their relationship of almost being brothers instead of master and apprentice, when the Jedi explain not to form attachment and embrace feelings. The Jedi are a mess). 

Never once did Obi Wan consider joining the dark side. After all the traumas he experienced, he chose to remain true to his heart. And that’s what exemplifies a true light side user. Not even just categorized as a Jedi. Was he at fault for training Anakin improperly, absolutely. Was it his fault for not being ready to train Anakin, of course not. Had Obi been given more time and wisdom with Qui Gon, things would have been different.