If historical reference is any guide, I could keep an immaculate written record of my life and the most historically interesting/important things would still be my grocery lists.

Journals don't give us as much insight into an age or time as it does insight solely into the author. While it might be interesting to your future progeny, "Great-great-great-great Grandpa AzJon stared into the pointless void again" isn't really a thrilling read. Dates, places, prices, and inventories are what compose the vast majority of historically relevant first hand accounts. So, in that respect a "to do" style journal would probably be more historically "significant" than a "my thoughts on the page" account.

If you want to be extra dramatic about it, you can burn your journals on the 15th of February, i.e. the Roman feast of purification. From Etymonline:

"late 14c., ultimately from Latin februarius mensis "month of purification," from februare "to purify," from februa "purifications, expiatory rites" (plural of februum "means of purification, expiatory offerings"), which is of uncertain origin, said to be a Sabine word. De Vaan says from Proto-Italic *f(w)esro-, from a PIE word meaning "the smoking" or "the burning" (thus possibly connected with fume (n.)). The sense then could be either purification by smoke or a burnt offering."

Seems reasonable to offer your journals to the pen gods.