There is a famous saying in the Bitcoin world, buy the rumor, sell the news.
I think that's similar to what you stated, and actually that saying is still relevant until now, although currently due to institutional investors, the market is less volatile compared to the past few years. Still, it's good advice to remember so we don't get caught up in the hype and end up selling at a loss, after all in trading, timing is important so we cannot afford to be greedy.
Same with "buy low, sell high"; it's that simple. If some coin ends up getting super high, buying that makes no sense at all. I think the best thing we could do, at least right now, is realise when the bear markets happen and when bull markets happen.
If you think that it is a bull period, then you end up doing something regarding that. Right now it is not a full market, but it is still smart to check the market for any coin you want to buy, and if you are doing it properly, then you should not be worried about it. If it is not above ATH yet and is still low, just like Bitcoin, then buying something is not a bad idea just yet. Of course, it could have been better if you bought a little earlier, but it is still better than buying even later.