Is it permissible to break off an engagement from a religious and well-mannered girl due to a lack of psychological comfort with her, and fear of repeating the same experience in the future, knowing that the young man has been suffering from psychological distress and tension since the beginning of the engagement?

Breaking off an engagement is permissible because it is merely a promise. Either party may break it off whenever they wish. Sheikh Ibn Baz was asked about the ruling on breaking off an engagement, and he replied: "There is no harm in that... As long as the contract has not been finalized, everyone has the option." Breaking off an engagement is permissible, especially if there is a need for it, but it is disliked without a need. There is no injustice in merely breaking off the engagement from either party to the other. It is advisable to be deliberate and not rush into breaking off the engagement, as the success of a marriage does not require a specific emotional feeling. If the girl is religious and of good character, seek Allah's guidance through Istikhara; for what He chooses is the most suitable, and what you feel may be mere whisperings (waswas), so seek help from Allah and remember Him. If you ultimately decide to break off the engagement, it is permissible.