In the Star Wars: The Clone Wars film, Yoda assigns Ahsoka Tano to Anakin Skywalker as his Padawan with a plan to teach the young Jedi Knight about letting go of attachments, but she'd go on to ruin that plan. Though Yoda is a true Jedi Master, his lack of foresight in this instance may have been one of the root causes for Anakin becoming Darth Vader.
In Clone Wars, Ahsoka arrives and is first believed to be Obi-Wan Kenobi’s Padawan, however, it is not to be so. She is assigned to Anakin, who believes he is better off without a youngling weighing him down. It turns out he could have been correct as, over the course of the first season of The Clone Wars, he proceeds to form a strong bond with the young Togruta. The two form mutual respect and grow in turn, and the relationship forces Anakin to examine his own Jedi methods, and view the world and the war through new eyes. The issue is that Anakin’s habit of forming bonds is stronger than the average Jedi. Once that bond is formed, he is unable to let go.
Yoda probably assumed that helping a young Jedi find her footing among the order would force Anakin to take an in-depth look at his own training and actions. He would be able to on what he had learned, and step into the role of teacher, modeling the Jedi behavior that was expected. The assumption is that by helping Ahsoka become a Jedi, Anakin would be able to watch her successfully from one level to another, and could then let her go off on her own knowing that he had done all he could to help her. The key being: “Let go”.
Anakin and Ahsoka’s relationship becomes especially clear early in The Clone Wars, as in season 2, episode 5 “Landing At Point Rain”, when they are having a contest over how many battle droids they can kill (reminiscent of Gimli and Legolas in Anakin struggles with his Padawan Ahsoka and when to let her proceed on her own and grow, and when to protect her. Over time, they come to trust each other as family and are bonded even closer throughout The Clone Wars until Ahsoka’s final predicament as a Jedi.
If Yoda had truly wanted Anakin to succeed in his endeavor as a teacher, the proceedings at the end of The Clone Wars, season 6 should have gone much differently. When the Jedi Temple on Coruscant is attacked from within, Ahsoka is wrongly blamed by the Jedi Order – including Yoda – and left to her own devices as she attempts to prove her innocence. The council does not trust her, presumably because she is Anakin’s Padawan and takes after him in her disregard for the pomp of the Jedi and their dogmatic rules. This whole debacle only serves to make Anakin question the Jedi Council more than he already does, and when Ahsoka is proven innocent and decides to leave the order, he can only share that sentiment. Instead of celebrating her success, he is forced to watch her walk away and, once again, a relationship is torn from him and the Jedi are partly to blame.
In the end, rather than allowing Anakin to feel a sense of accomplishment in guiding a Padawan to Jedi Knight status, he is left with deep feelings of anger, regret, and betrayal. And without Ahsoka by his side as a voice of reason and innocence, he is left alone as he works with the Jedi to bring The Clone Wars to an end. Yoda’s plan backfired drastically. In trying to bring Anakin closer to the light, and show him the path of the Jedi, he made a decision that ultimately caused a rift between Anakin and the Order and led him a step further on his journey to the dark side.
