tradAs with moving the stop to breakeven: we will not say whether you should. We will say what can be measured, because that is where the discussion becomes useful rather than a matter of conviction.
WHAT A PARTIAL DOES, mechanically. It reduces position size before the target. It therefore reduces the gain on trades that go all the way, AND it reduces the loss on those that turn back after starting well. It is a trade, not an improvement: you pay performance on your best trades to buy consistency on the average ones.
SO THE QUESTION IS NOT « IS IT GOOD », it is « WHAT DOES IT COST ME ». And that has a number.
The reading that settles it: among trades that went past the level where you take your partial, what share reached the target? If that share is high, the partial is expensive, because it cuts the part of the position that was about to work. If it is low, it saves you as much.
TWO MEASUREMENT TRAPS, which distort the comparison more often than people think.
The first: comparing a period WITH partials to a period WITHOUT. Those are not the same markets, nor the same trader. The only solid comparison replays both rules on THE SAME history.
The second: looking only at the average result. A partial also changes the shape of the curve, so the largest drawdown and the length of streaks. Two rules can return the same average and be very differently liveable.
And there is one reason that resists measurement, and it would be dishonest to leave it out: many people take a partial in order to hold the position instead of closing it entirely. If that is what stops you from cutting everything too early, the numbers do not tell the whole story.