That's not how it works... If you believe that "upward momentum" or "downtrend" mean something, why don't you go long now and sell at the first signs of weaknes

That's not how it works... If you believe that "upward momentum" or "downtrend" mean something, why don't you go long now and sell at the first signs of weakness? Easy money, right? In reality, there are no simple and exploitable rules like this.