People know what a flow state is. Here are some tips to keep your mind within this zone:
Listen to a repeated score, must be background music style. Looking for game music as they have a genre called BGM that are played in the background which simulate this flow state but for gamer. If it does so for gamer (Making them go on and on for hours), it does the same thing for your working brain too.
Have a scheduled break point to remind yourself you are moving ahead, not swimming endlessly and pointlessly without a marker.
Make sure to setting a group to blame you if you cannot reach the goal. This group could be anyone, preferably those who are willing to give you spanking if you fail, and are willing to have sex with you if you finish the deadline.
Have Coffee by your side, but no more than half a spoon of sugar. Sugar sooth the brain and make it fall asleep.