The basics of bullet journaling is simple: grab a notebook and a pen and just begin. A bullet journal is helpful in creating indexed calendars, to do lists and note collections, it is the ultimate DIY planner.
Journaling is a great daily habit. It helps focus the mind and get rid of things that bother you. It can be used for mindfulness, achieving your goals, emotional intelligence, boosting your IQ, memory (Diy Step Link)
I have a whole notebook full of things and pictures that make me happy. When I'm feeling really low I pick a page at random and read it then I spend the day appreciating those things. Works every time.