History doesn't get written by the victors, it gets written by the historians. So it is possible to significantly influence people's understanding of history simply by being the one who records it. I often am probably the only one who has written of a party attended by people, and so 50 years from now my record will be the only thing anyone knows of the event. In a sense by caring enough to write it down, I have elevated the historical importance of my perspective on the event, since mine is the only perspective people will see.
History tends to be thought of as the chronicle of very large, important events, like the battle of hastings or world war II. But for individual people, the history of their own lives, their immediate ancestors, or the neighbourhood in which they live can be even more fascinating and also useful to future planning.