Many of you maybe know (or have heard) about DayOne: it's one of my favourite Apps. Basically it's a Journal where you can write everything, from your daily routine to your thoughts (personal thoughts). I love it, because it's a place where I can annotate all the things I want, without filters and sometimes it helps, because helps you to exteriorize things or thoughts that are hidden in your mind and you cannot focus clearly. It's really nice and incredibly helpful. Furthermore it's a source of smiles: do you remember that fucking night when you were angry with your friend about that stupid thing? Yes, thanks to DayOne you can re-read the words you've written and laugh about that stupid misunderstanding and never do that again. It simply helps.
There're lots of uses for DayOne, I suggest you to read DayOne blog to better understand how to use DayOne or better if you already use it, catch new great ideas about how to improve.