When you stop having a realistic view of porn. If you are using it as a simple pleasure and exploring sexual expression, there's no issue.
If you see you are using it too much, and is causing you problems, you may need to be aware that you are developing an addiction like any other.
If you start purposefully avoiding it even at the cost of your own comfort and stress relief, saying things like "porn wrecks your mind and sexuality", you are entering the current conservative, frustrating young people to manipulate them territory.