You're exactly right here.
The internet is full of distractions and one of the biggest reasons why many get addicted to the computer when they are under an extreme amount of unreality and stress. It becomes an entire world of its own, which is partly why I believe it is such an easy tool for grounding yourself. In small doses, this can actually be really great, but staying on the computer for longer periods of time may create adverse effects on your depersonalization.
For me, my greatest tool was grounding techniques.
What this aims to do is stop the introversion that many face with overwhelming emotions and unreality. It projects it outwards, which can alleviate the symptoms of depersonalization / derealization while maintaining a firm grasp on reality. This may not work for you immediately, but continuing to do it whenever you find yourself on the verge of panicking can really help perpetuate positive thought processes when coming under the weight of this kind of stress.