I've kept a diary for over twenty years, starting because I wanted to stick things like notes on films I'd seen in one place. I write most days, but not every day, and it's a mix of feelings, comments on stuff happening in the world, book and media review, holiday diaries etc. I write in A4 lined volumes, and am now on (checks) number 31. It still fulfills its functions of recording something I enjoyed, but is also very useful for feelings splurging at times. You could give it a go and see what it evolves into - a factual record or walks, thoughts on current events, a sewing journal, personal exploration - you don't need a clear image in order to start.