"Truth enlightens the mind, but won't always bring happiness to your heart."
– The Hidden Enemy, Season 1
Clone Sergeant Slick knew how it felt to be discouraged by the truth, too. It was surprisingly short into the war before he realized the truth, or at least a perceived truth, about the Jedi's treatment of him and his men. Apparently, the Jedi used the clone troopers as slaves who did their bidding, and only their bidding, and never gave any of them something more. His mind was enlightened by this information, and he thought about a way to break free of the Republic clone army.
Unfortunately, the truth didn't make him happy at all, and in his unhappiness, he didn't think rationally. As a result, he looked for his escape from the army through illegitimate means, namely, through Separatist connections, and put some of his brothers at risk during the Battle of Christophsis. In the end, he was caught by his superiors and taken into lock-up, and now, as he stewed in prison, awaiting a likely execution, knowing about the way the Jedi took advantage of the clones' obedience made him unhappier than ever. And it certainly didn't help when Rex and Cody told them that if he loved his brothers, he wouldn't have put them at risk.
"Don't be too eager to learn the whole truth of something if you're not ready to endure its meaning. Truth makes people smart, but it also makes them sad and miserable sometimes."