It is important to be aware that even though thoughts are invisible to the
five physical senses, they carry real energy that has real effect on your
life and even the world.
Thoughts that are not congruent (harmonious) with love contribute
negatively to your life and to the world.   While thoughts that are congruent
with love may contribute positively to your life and to the world at some level,
at a deeper level their entertainment distracts from awareness (more about
this later on).

Daydreaming and fantasies are also thoughts.   If you entertain
daydreams and fantasies that are not congruent with your true Self
(that is Love), they can weaken you and cause problems for you
that may even manifest in the physical world as poor health, accidents,
and other negative occurrences; even if they don't manifest in the physical
world, they still create issues in the subconscious world (including emotional
blocks, energy system fragmentation, nervous system fragmentation,
weakened spiritual self-defenses, possibly preventing proper connection with
Divine Loves [Gods], etc.).

Examples of incongruent (disharmonious) thoughts are fantasizing
about: revenge; being violent towards someone; sending someone to hell;
a harm happening to someone; battling someone; having sex with someone
against his/her will; hurting nature (animals, trees,...); joining the military;
sadism; masochism; etc.
Children, especially boys, playing with toy weapons, having pretended
battles and fights, is also using disharmonious fantasies for entertainment.
That can have even quite a negative impact on their growing up/health.
(Even seemingly funny cartoons that use the concepts of violence,
such as trying to shoot the rabbit, blow up the road runner, transformers
battling it out, etc, affect children negatively, because they use
the concepts = fantasies = thoughts of violence.   Blessed is the child
that doesn't watch TV/movies.)

While positive, loving daydreams and fantasies carry positive energy,
their entertainment affects your awareness.   When your mind is busy,
you are not centered in your true Self - you are not aware.
The most positive state of being is being fully aware.   Thus it is the most
beneficial to ignore the mind's attempts to daydream and fantasize.
If a daydream or a fantasy begins unraveling in the mind despite your
intention to be centered and aware, it is beneficial to just observe it
with detachment; that is not getting involved in it emotionally.
The moment you start participating in the daydream or fantasy by either
going on with it or trying to fight it, you empower it and allow it to control you.
The reason why a daydream or a fantasy comes to the mind can be an unresolved
issue in the subconscious, or something is trying to get your attention for whatever
reason.   The best way to bring to light what is causing it is going to a doctor that
performs Neuro-Emotional Technique (NET).
Addressing the other two parts of Good Health Trinity is vital to reducing
the busyness of the mind. Also very beneficial is the silent meditation
(when you are congruent with it - please see that page), and prayers.