I use the app Day One to journal. It’s available for iOS and macOS. I suggest committing to journaling for 5-10 minutes everyday for at least a week. A week gives you enough time to observe patterns in thought and observations about yourself.
I use a planner for work and personal life. I am not big on writing a paragraph about what I did in a day. The planners help me stay focused on the tasks I need to do while documenting my daily activities.