What happens when you drift off into periods of reflection and daydreaming? There is some sense of letting go of your usual awareness of the world, and allowing something else to happen. Evidently your conscious mind needs to take a holiday every so often.
Some writers say they connect with good ideas during the daydreaming state, and it is fuel for their creative process. Freud thought the contents of the unconscious mind are more accessible to writers when they let their minds drift.
Daydreaming can also be a habit that interferes with writing. If you tend to fall into a waking dream to avoid facing challenges in your writing, you have probably learned todecrease your experience of stress and anxiety in this way. The questions to consider are: Where does your mind go? How long does it go there? and, Do you return to your project in a timely and productive way?
If your mind goes far away into reveries that have nothing to do with your writing, and if this happens frequently or for lengthy stretches of time, it may be a writing productivity issue you ought to address.
When you are lost in a daydream, your mind is following unknown impulses that may or may not be contributing to your writing goals. The key is to notice whether your daydreams inspire your work or lead you astray and waste time. If it is the latter, there are ways to become more aware of this process and bring some measure of control to it without shutting it down.