A filename gives you a clue, but it does not tell the whole story. Before opening an unexpected attachment, think about where it came from and why it was sent. For practice, use documents you created yourself.
Keep the source in mind
A file from your own work folder and an unexpected download deserve different levels of caution. If someone you know sends a surprising attachment, check with them through another familiar channel before opening it.
Separate work from experiments
Make a learning folder for harmless examples. Copy a document before trying new editing tools. Keep the original until you have compared the result, and use filenames that make the relationship between versions easy to understand.
Inspect before sending
Open the exact file you plan to attach. Review the whole document for personal details, extra pages and information unrelated to the request. Check the recipient as carefully as the file. A correct attachment sent to the wrong person is still a mistake.
Try this yourself
Create two versions of a short note, then choose the intended version as a practice attachment without sending it.
Check your understanding
What checks helped you recognise the right document?