Left to free writing, journals drift into venting or go silent on the days they matter. A fixed set of questions removes the decision of what to write and makes entries comparable over time.
A useful set is small. Before the session: how did I sleep, how do I feel, and which rule am I most likely to break today? After each trade: was this a setup in my plan, did I follow it, what was my risk in R, and what one word describes how I felt? After the session: what is the one thing I did well, and the one thing to change tomorrow?
Good prompts are answerable in a sentence and ask for facts or choices, not for self-judgement. What did I do is better than why am I so undisciplined. Prompts that invite harsh self-criticism tend to make people stop writing.
Review the answers, not just the writing. Once a week, read the entries in a row and look for repeated phrases, repeated rule breaks and the states that come before costly trades.
Change the prompts rarely. If you rewrite the questions every week, you lose the ability to compare one week with another.