A Zettelkasten is a tool to extend someone’s mind to a realm where working memory is not an issue. As such, it is often referred to as a Second Brain since it represents a mind and thought map of oneself.
To truly be useful in that context, it only works if every idea — no matter how elementally obvious or controversial — is allowed into the Zettelkasten. It is only there in the context of “more established” thoughts that we can begin to process these fleeting ideas and feelings.
To return to the garden metaphor, we don’t know where or if a new plant will fit in our garden until we’ve had time to examine it in order to prune it or water it for growth.
Extending this idea to journaling, we should expect to find raw and honest thoughts and feelings that don’t necessarily reflect reality.