My Mum writes in a diary every single night. I was reminded of the diaries when I recently stayed and went into the cupboard under the stairs. On the shelves she has diaries going back to when my brother and sister were small, so she must have around 50 years worth at least. As far as I'm aware she has never missed a entry, some days the entries are short and just about the weather or what shift she worked that day but other days you have the entries about birthdays, deaths, births, first steps, ...