Pacing: When to Hold a Shot and When to Cut
Answers how to pace a video edit

Pacing is usually taught as a matter of rhythm: cut on the beat, keep the energy up, do not let it drag. That advice produces edits that move and do not hold, which is the specific failure of a film that feels nervous.
The other half is knowing when *not* to cut, and it is harder because a held shot looks like a mistake until the film is finished.
The three places a shot has to be held
The first shot of the film. A viewer needs a moment to work out where they are before they will follow you anywhere. Cutting at a second and a half out of an instinct to get moving costs you the next thirty seconds, because nobody has settled. Two and a half to three seconds. Slow enough to be a decision.
The shot after the turn. Every film has a moment where the argument changes: the demonstration gives way to the proof, the problem to the solution. The cut after that moment wants to be late, not early, because the viewer is still processing what just happened. Cutting on the beat here steps on your own point.
The last shot before the card. Whatever the film asks for at the end, the last image needs a beat of stillness or the ask arrives while the audience is still watching the picture. This is the single most common thing missing from an edit that is otherwise fine.
The four excuses for cutting
Because the shot is boring. Boring for whom? You have watched this footage forty times. The audience has watched it once, for two seconds. Boring is usually a word for "I am tired of it".
Because the music moved. Music is a grid, not an instruction. A cut that lands on a beat but interrupts an idea is worse than one that lands a frame late. Let the beat pass sometimes. It reads as confidence.
Because the last take was better. Nobody is comparing takes. They are watching one film. The better performance that arrives mid-word is worse than the adequate one that arrives on a full sentence.
Because the timing looks empty. This is the one worth taking seriously, so it needs the real test: mute it. If a held shot feels empty without sound, it is empty with sound too, and the answer may be to hold it longer rather than cut it.
How to tell whether the pace is right
Watch it once with the sound off and once with the picture off. Two different films, and both should hold.
Then watch it at double speed. Pacing problems are obvious at 2x and invisible at 1x, because at 1x you are watching the content and at 2x you are watching the shape.
Then watch the first ten seconds, stop, and try to say what the film is about. If you cannot, no amount of pace in the remaining twenty will repair it.
The uncomfortable version
Most edits are cut too fast, and the reason is not taste. It is that an editor who has watched the footage a hundred times has lost the viewer's clock. The rough cut that felt glacial to you on Tuesday will feel brisk to someone watching it cold, and the note you get is "it drags".
Which is why the rough cut should go to one person who has no idea what happens next. Not for their opinion, but for their timing: where they look away is where you cut too late, and where they ask a question you already answered is where you cut too early.