Express Helen's feelings that she had while writing a diary.

In chapter 2 of her memoir, called "Personality," Keller writes in her diary in 1894 while attending the Wright-Humason School that she wants to learn four things: to think clearly, love sincerely, act with the highest motives, and trust God. As she puts it:

I find that I have four things to learn in my school life here, and indeed, in life—to think clearly without hurry or confusion, to love everybody sincerely, to act in everything with the highest motives, and to trust in dear God unhesitatingly.

Earlier, in 1888, Miss Sullivan had encouraged Helen to keep a diary. Helen did so, and in it she recorded a feeling of love towards blind children she had met.
Perhaps the most important diary entry comes in the year 1892. In this entry, Helen records being troubled, saddened, and grieved that she had, without meaning to, plagiarized a short story she thought was her original composition. She cries and doesn't know what to think about having made such a mistake. She didn't think people could make such mistakes. She writes:

My heart was full of tears, for I love the beautiful truth with my whole heart and mind.

All three of these diary accounts show a girl aspiring to goodness and trying to be loving, sincere, and kind to others. She doesn't use her diary, at least not in these instances, to record angry or negative feelings but to record her best intentions and her sorrow when these fall short.