I used to use this when freelancing and a big deadline was approaching, I found it very helpful. It felt like I could get at least twice as much done in a day.

I used to use this when freelancing and a big deadline was approaching, I found it very helpful. It felt like I could get at least twice as much done in a day. However I stopped using it after getting into a minor motorbike accident. Another motorbike was driving on the shoulder (pretty typical in Thailand) and I didn't spot her while turning at an intersection, even after checking both directions. The tunnel vision side-effect is no joke!