Notes
For quick notes in my day-to-day life I prefer using Apple Notes, as these are quickly available on all my devices and synchronize over iCloud.
Recently, I have started adopting the Forever Notes. My favorite concepts of the system are the home note with links to hub notes, which in turn include backlinks to the home note. This allows for swift navigation between topics. I also keep a note for each of my projects, so I can quickly write down ideas when they come to my head. Active Projects are linked in the home note too. For Journaling, I am still using Day One.