The problem with the occlumency lessons were several fold. First, Harry, finally faced with an adult who was privy to some of the things he was starving to know, was consumed with finding things how to which he felt he had a right. This was also the reason he looked into the pensieve. He thought that information about the Department of Mysteries was openly being denied to him. Harry wasn't goading Snape; he just wanted to know things and Snape was too busy falling back on his titles. "This may not be an ordinary class, Potter,' said Snape, his eyes narrowed malevolently, 'but I am still your teacher and you will therefore call me "sir" or "Professor" at all times.'" What was more important here, learning or the power balance? Adults think it's okay simply to demand things of children without putting them in context; it is not. Children are not robots; they are small humans who rely on these people to nurture and teach, not demand and manipulate. How can you ever hope to increase children's understanding of a world without context? Secondly, their mutual dislike was calculated to ruin any progress they might make. Snape does not care for Harry and he makes this plain over and over again; he only does all this in the name of his love/obsession with Harry's dead mother. Consider, would he even have switched sides if Voldemort had decided to target the longbottom family instead of the Potters? Did you not understand the significance of the doe patronus? Snape hates Harry on sight, for things over which Harry has no control and could not change if he wished to. Have you any idea what it is like when an authority figure takes against you for no reason that you can control? I do. I grew up with such people. Authority abuse is very different from playground bullying because the abuser is able to cloak their behaviour in their authorty while protecting themself from possible censure. Thirdly, Snape failed to explain things adequately to Harry. He could have explained that his scar might hurt worse in the short term, why this would be and he could have shown Harry some meditation techniques to help him empty his mind. He did none of that. Harry said repeatedly that he did not know how to do what Snape wanted of him but Snape did not listen. He was asking for guidance which he did not receive. This is a teacher who suffers from the curse of knowledge: the idea that he can't adequately pass on his knowledge because it has always been obvious to him and he cannot conceptualise that it isn't to everyone else. I have suffered teachers in this mould. Each time you have to be alone in their presence there is a sense of dread which only engenders fear, and which encourages neither motivation, learning, respect or any wish to practice. I met these people more than five decades ago and I am only now discovering the extent of the damage caused by that long-term interaction. Adults do not always know better than children, particularly when they are emotionally immature adults. Respect must be earned. If you have to rely on a title in order to demand respect you aren't doing enough to earn it in my view. 'Because I said so' has never been a legitimate reason to ask anyone to do anything because that statement is about power, not humanity.