No matter what the current price is, people always think there will be better opportunities to either buy or sell. It's a vicious circle. I am not sure why you believe the price will drop to $20-25k. If the value drops to $25k, you will be waiting for $20k. If it drops to $20k, you might think it's better to wait until $15k. Too much waiting, and you'll miss the train. If you have money to invest and you are willing to do it, go ahead. It's the same when you are selling. If you have made some profits that you are satisfied with, dump your bags and get back in the game with the next cycle.
You are right, actually such a thought or strategy is like a loser who always expects the bitcoin price to fall lower to execute it. They don't think because some people or investors would expect the opposite and they hope that the bitcoin price will not go back down and their big hope is that the bitcoin price will continue to be bullish.
Be a smart investor by buying when you have the money without having to wait for the price to drop to buy it, and when it does, it can't hurt to buy it back. You can buy bitcoins anytime and never put it off because sometimes this way of thinking is wrong, because the price of bitcoins is not easy to predict and if the price of bitcoins keeps going up, you will not regret it.
So my advice, buy it when you have the money that day, and you can buy it back if the price drops back and stays that way and for long term goals. And if you do it for the long term, you don't care about the price of bitcoin to buy it.