[PYenner]

The advice of a trader with 20 years experience (Simon Harris) was-
"Don't ever regret taking a profit, only to find that the price continued to move your way".
To me, taking a profit is beating the game, doing your job.
Pat yourself on the back for getting it right, first and foremost.

The question really splits into two parts.
For the first part, when a swing goes as expected, I am happy to get 80% or more of the expected movement and to achieve safety from an exit that might be a bit early. That is the basic daily trade, the one you have "signals" for.

The second part, when the movement goes further than expected, has to be treated as a second strategy and you can only trade such a strategy if you have a signal for it that can be relied on. If you don't have such a signal then you have done all you can do for the present. The aim is to go in search of signals that you are currently unaware of. They may exist, they may not.

But until you have a relible signal you should stick to the strategy you have because gambling leads inevitably to losses.

To me, leaving a portion of the trade running in the hope/risk of a windfall is gambling and likely to be a waste of time and effort, a distraction from the real issue which should be about looking for a usable signal.