This particular task has some challenges embedded within it. Diary entries are usually reflective of sensitivity. Someone who has a sensitivity towards society, themselves, or others feels compelled to write down their thoughts. The question here is whether someone who is desensitized would be able to compose their thoughts in a diary format. If so, what would it look like? A diary entry, in general, is composed of an individual's reflections about the world and, perhaps, their place in it. In a diary entry of someone desensitized to their world, it seems that sentences would be declarative, informative, and short. There would be little in way of reflection or expression because such elements contain a sensitivity that someone who has been desensitized lacks. This would be the condition that the Party wants out of its citizens. Lacking reflection and lacking the ability to ponder about their condition of being is the end goal of the mind controling elements of the party. It is for this reason that diary entries would be violations of thought control and discouraged. It is also for this reason that the task is tough to compose in the spirit of Orwell's work.
In progressing with the task, I would focus on the Parson children. Winston's neighbors live in constant fear of their children as they have become indoctrinated into the party's thought apparatus. They are tools of the Party. Their uniforms and the ability to demonstrate loyalty to the Party are all that matter. They have become desensitized to everything else around them. Mrs. Winston looks much older than she is because she is constantly afraid of her children turning her in. She lives in a state of perpetual fear of her own children because they have become desensitized to the connection between parent and child. The children embody desensitized world of the Party's desires. It is here where I think that the diary entry could reveal much. Essentially, the child who believes in only the party would write about how their being is the Party. Any response to stimuli they would encounter would be viewed in the frame of reference of love of the Party. They would dwell on what they would do if they encountered someone who lacked loyalty to the Party, or what they have done if placed in this situation. For example, Tom Parson's daughter betrays him to the Thought Police for talking in his sleep. Detailing what a desensitized child would do for the Party or what they have done in the name of the Party would be expressed in a diary entry, for even if it was caught by the Thought Police, it would be an expression of the utmost in loyalty to the Party.