"What error should I avoid?" is a prevention question: you want to understand where your current move might slip. The cards do not read the future as a script, but can indicate the type of symbolic error most likely given your current state.
What the reading reveals
The Hanged Man shows that insisting without changing perspective may be the main risk. Seven of Swords warns against dishonest shortcuts. Five of Wands advises not to enter useless conflicts. The Devil signals the risk of staying attached to what is toxic for you. The Moon reminds not to act in confusion, before seeing clearly.
How to use the warning
Identify the error named by the cards and bring it to a concrete example of your life: where do I really risk this error this week? What small gesture can I do not to commit it? Often noticing the pattern is enough to defuse it. The cards function here as an attention bell.
FAQ
Do the cards tell precisely what NOT to do?
They indicate a symbolic quality of error. The concrete translation is your work.
What if I have already made the error?
The reading can help recognize the pattern to avoid repeating it.
Can I read before a choice?
Yes, one of the most useful uses. A "warning card" before an important decision is a good awareness practice.