"Buy low, sell high" is one of the most popular memes in the investment and trading world. And obviously, it does make sense, who wouldn't like to buy low and sell high all the time? I found this to be quite a helpful advice to invest in stocks for example. Wait for a crash, buy it and sell again when prices are back to old highs.
Of course, the problem often is to figure out what's actually a low price and what's a high price. You can also buy high and sell higher to make a profit, which is how trend following works.
So what's the real deal here? I think the actual question to ask is "who's going to buy after me?" or "who's next in line?". Will there be enough traders willing to buy after you did at a higher price? Or if you're short the other way around, will there be sellers standing in line to sell after you did or not?
Think about it. To make a profit that's exactly what needs to happen. If you buy at $100, the only way to make a profit is if there are buyers willing to buy at higher prices. If they don't bid it up after you and you find someone to sell to at a higher price, you won't make a profit. Simple fact most traders are not really aware of.
Obviously, there's always someone who's gonna be the last in line. Someone is going to buy the high of the day/week/month/year/all-time. In poker, there's the popular saying that if you don't know who the patsy is in the round after 30 minutes, it's probably you. That same idea applies to trading. If you don't know why other traders are probably willing to buy at a higher price after you during the day, you might be the last one in the order book to bid at such a high price for today.
Because of that, it's always helpful to ask yourself "Who's gonna buy/sell after me and why?". If you can't answer that question it might be best to skip the trade!