* To protect him from Voldemort's mental attacks: Voldemort, through his connection to Harry, could invade his mind and attempt to influence him. Occlumency would help Harry build mental defenses to resist these intrusions.
* To prepare him for the future: Dumbledore knew that Harry's destiny was intertwined with Voldemort's and that he would likely face more mental battles. Occlumency would be a crucial skill for surviving and defeating Voldemort.
* To help him understand Voldemort's thoughts: Occlumency involves delving into one's own mind and understanding its workings. This could potentially allow Harry to gain insight into Voldemort's thought processes and predict his actions.
* To control his emotions: Occlumency teaches the ability to shut out and control emotions, which can be a powerful tool for Harry, who is often overwhelmed by his own feelings.
* To shield his mind from Snape: Snape, under Dumbledore's orders, was monitoring Harry's mind for Voldemort's presence. Occlumency would allow Harry to control what Snape could see and protect his privacy.
However, the lessons were ultimately unsuccessful for Harry. He struggled with the complex techniques and his strong emotional connection to Voldemort made it difficult to shield his mind completely.
Despite the difficulties, Occlumency lessons served a purpose in Harry's development. It helped him learn about his mind and his connection to Voldemort, and it contributed to his eventual triumph over the Dark Lord.