Journaling has been around for a very long time and people use this in various ways, particularly to note learnings from days they've had, seminars attended etc.
A practice journal for golf is a great way of being able to plan out your session, so you can help yourself stick to what you want to get out of that practice.
A highly important element to this is making sure you note down at least three things you learned from the session. This will help learnings from your practice ingrain even more.
Soon you'll have a a great reference source of not only various practice plans that you can revisit in future sessions, but also remind yourself of what you learnt... this can only help you improve your game!