You do not need a perfect notebook or a big idea to start journaling. Open your journal and write one sentence about how you feel right now.
If words are hard to find, try a question: What was on my mind today? What do I need to feel better? What do I want to remember about this day? Answer honestly, even if it is only two lines.
Returning to your notes over time can help you notice changes and patterns. Writing is personal: find a rhythm that feels comfortable to you.