An Observation

I have made an observation over the last couple of months.
Whenever we have a day like the above , ie when the index spikes up at open and then stays flat ie constant the rest of the day.

Then the next day or the day after will be a negative day.
This has been see n many times and works - I dont know why but it does.

Let us see if this is a fluke or is there some market structure behind it that we dont know.