ATH means all time high so when the btc rise up above the past high price , we can considered it all time high we can monitor the price in so many exchange and there are also some price tracking apps, so there is no problem on tracking the current price the problem is we don't know when BTC will drop down drastically and we will end up losing if we don't have patience to hold.
It is true that bitcoin investment requires patience even if the price of bitcoin goes down those who can wait patiently will reap good profits. The stupidity of selling will rise again even if the price goes down. Bitcoin is reaching its all time high and creating incredible milestones for the cryptocurrency industry with bitcoin's new ATH.
Yeah being patient enough must be too hard for most investors, normally if it was something that goes up small by small, like for example gold does require a lot of time to go up a lot, you will have to spend a lot of time and that has to be the most important thing, and we should definitely consider the situation changing at all times. I personally believe that the best thing to do in this case would be basically arranging bitcoin to be straight forward if it was just patience.
However, the difference is that, while bitcoin may go up more than gold, it could also have a period where it crashes in the middle, meaning while you wait, you see it crash many times, and then you get richer, so it is a lot more emotionally damaging to keep holding it, and makes people scared.