I bought at the ATH too, but it does not mean you have to be panicked about the price dropping. If BTC has achieve that ATH today then it will come back to that price one more time in the future also. So why fear so much?
Just hold and to overcome the losses which is temporary, you can buy more at lower values.
The thing about buying at ATH is that, if you are careful about what you are doing, you should be fine about it anyway. For example when you buy bitcoin at 20k, which was the ATH and sold today, you would still be in x2+ profit today, that means buying at ATH doesn't mean that you are doing a bad thing, and I have said repeatedly that bitcoin moved beyond 1400 easily last time to go to 20k so breaking ATH and having new ATH would always mean something easy, to have a bigger and huge ATH was inevitable.
However one thing I am 100% sure about is that if we fall down now, if this is a 2018 like fall, and we will only recover few years down the line, it is still not a bad thing to buy now, why? Because you can keep buying, buy for 3 years and the next time it goes up, you will be in a much much bigger profit for sure, that is what you should focus on, not "what profit I am making now" but "what profit I can make in the future"