A signal says "buy here." A fill is the moment your order actually executes. People obsess over the signal and ignore the gap between the two — which is exactly where a strategy's paper edge tends to evaporate.
What lives in the gap
Between seeing a signal and getting filled sits a stack of frictions: the lag to read it and react, the hesitation ("is this one real?"), the sizing decision made in the heat of the moment, the chase as price moves while you fumble, and the slippage on a rushed entry (slippage). Each one shaves a little off the theoretical result.
Why it hits signal services hardest
A signal service hands you an alert and stops there — everything in the gap is your problem. Two people trading the identical signal get different results because they cross the gap differently: one hesitates and chases, the other freezes and misses it. The alert was never the hard part (why signal groups disappoint).
The signal is the easy 10%. The fill — the timing, the size, the discipline to actually pull the trigger the same way every time — is the hard 90%.
Closing the gap
The only reliable way to close the gap is to remove the human from it: define the rules in advance and let software execute them the instant conditions are met, identically every time. That's the difference between a signal and a system — one suggests, the other acts (signal vs execution). It's the entire premise behind an execution tool like NoVo: you set the rules and risk; it crosses the gap for you, without hesitation, in your own account. See manual vs automated execution.