Yes i know that, same if i have 21 reds in a row, it still is 50/50 situtaion, but i have never seen any report for the last 300 years any case with 300 reds
That's because 300 reds is only one of the multitude of possible patterns that can and will hit. However, what you're over looking is that fact that one extremely and equally rare pattern did emerge that was 300 spins in length! It likely just wasn't the pattern that you were looking for.
Which pattern is less likely to hit?
The answer is that they all have the same chance of hitting! And by the way, there are a gazillion of different patterns, of which one will emerge!
What should really blow your mind is if you think about what the probability was for those 300 numbers to have hit in the exact order in which they hit! 1/37^300th. Wow!!! Why didn't the casino report the event??? Of course the reason is because there likely wasn't anyone looking for that pattern. But then again, you never know. Maybe there was some old guy that was running a progression betting against that pattern ever happening again. Or, maybe he was betting for it to happen.
You must learn to put this in perspective in order to escape the event horizon of the gambler's fallacy.
Best of luck,