The default mode has a "prospective bias". Depending on the person, their history, and their biological dispositions, that prospection could tilt toward worrying or hoping. There are 3 different types of day dreaming: 

1. Positive constructive daydreaming: lots of playful, wishful imagery and plan-making thoughts.
2. Dysphoric daydreaming: lots of anguish and obsessive fantasies. 
3. Poor attentional control: hard to concentrate on anything

Research indicates that a disturbed DMN is a mechanism in depression. Our greatest source of suffering isn’t the default mode but when we get stuck in the default mode.

The wandering nature of the DMN can be harnessed for creative thinking. In a 2015 study, participants were asked to do creative thinking tasks. Results showed that creative thinking requires a combination of focusing internal attention and controlling spontaneous thinking. It underscores the fact that not all minds that wander are lost.

Suffering arises when people concretize the fleeting swirls of thought, especially around conceptions of self. Default-mode content involves an image of self, one that’s easy to become attached to. These self conceptions carry lots of emotional weight. We think that the image of the self is something real and not just an mental image. However, the self isn’t one thing, it’s an evolving construct of many different processes.  

According to Buddhist traditions, when we take it to be real when it isn’t then that causes suffering.

In cognitive behavioral therapy, that process of divesting realness from your mental chatter is called “decentering,” or thinking less that your thoughts are the truth about what’s happening and viewing them as an observer. The therapeutic interventions offered by psychedelics like psilocybin and LSD — which, at least in one trial, helped longtime smokers quit at a rate three times that of the best pharma drugs — seem to have a similar, though more sudden, effect.

The trouble that your DMS gets into seems to depend on how automatic your patterns of thought are. The key is cognitive flexibility: being able to more freely choose your mental habits, and have greater agency in your cognitive phenomena. CBT and even hypnosis could tame an unruly DMN.

Meditation also reduces activity in the DMN. It reforms the DMN so that the resting state becomes more like the meditative state, producing “a more present-centred default mode.” By investing more attention in the sensory world than in your narrative overlaying it, you might identify the former to be what’s true.