Attitude Towards Speculation and Fantasy
There are two methods to reduce thoughts: 

(1) Wisdom method, which is replacing unwise thoughts with wise thoughts. This will reduce the thoughts &amp; build the wisdom that stops the re-arising of such thoughts in the future. Examples of wise thoughts are exactly what you have posted, which is thinking to yourself: "These fantasies are delusional &amp; are a waste of time". 

(2) Concentration method, which is to use the breath to feel calmness. When the mind feels calmness, it will not be inclined to think unnecessary thoughts. 

Before the Buddha attained enlightenment, he generally used the wisdom method to reduce his unbeneficial thoughts (refer to MN 19). This is called 'yoniso manasikara' or 'wise reflection'. 

The mind is difficult to know clearly &amp; manage therefore this is a task we each much learn. The Dhammapada states:


  33. Just as a fletcher straightens an arrow shaft, even so the discerning man straightens his mind — so fickle and unsteady, so
  difficult to guard.
  
  36. Let the discerning man guard the mind, so difficult to detect and extremely subtle, seizing whatever it desires. A guarded mind brings
  happiness.


In your situation, the wisdom method is probably the best method since you ask lots of questions here about meditation, which shows you probably need to know your mind more. 

As for 'non-judging', the Pali suttas do not really teach the practise of 'non-judging' towards unbeneficial thoughts. In addition, fantasies themselves are 'judgmments'. Therefore, if the mind was really abiding in 'non-judgment', it would not be fantasizing about the future.