In 1 Nephi 6:3-6 we are told what things should be included in a personal journal.
3 And it mattereth not to me that I am particular to give a full account of all the things of my father, for they cannot be written upon these plates, for I desire the room that I may write of the things of God.
4 For the fulness of mine intent is that I may persuade men to come unto the God of Abraham, and the God of Isaac, and the God of Jacob, and be saved.
5 Wherefore, the things which are pleasing unto the world I do not write, but the things which are pleasing unto God and unto those who are not of the world.
6 Wherefore, I shall give commandment unto my seed, that they shall not occupy these plates with things which are not of worth unto the children of men.