Obviously, this is all premised very strongly on whether your system has any merit.
But let's assume it does.
You enter a trade, and then it moves (profitably or unprofitably) to a state where you are uncertain of the direction. Now it's a matter of exiting. If you weren't in a position, you'd neither buy nor sell here. So what should you do at the point where it's a coinflip for money? Something seems paradoxical in my thinking here...
A truly repeatable and thus (somewhat) testable system has defined entry and exit conditions. If you reach a point where you or your system doesn't know what to do, is it a system?
But that's the sort of advice that contributes to elite trader sounding more like a coach castigating his players than a community looking to hone a similar interest, so let me expand.
Part of the problem you'll run into trying to create a truly algorithmic system trading on bars as I imagine you would be given this sort of question is that bars change. If you were modeling, say, the bid and ask price processes using continuous data then each arrival time of a new quote or trade (poisson point process) could be considered an observation of a random variable. However, a bar has zero-several arrivals within a discretized timeframe, so if your system says something like: do X when price reaches Y, you're telling your system to perform an action based on an event that is actually unknowable at this time.
To illustrate this logic a bit less tersely: we're in the middle of a bar. Who's to say what the high, low, close, volume, etc. of this bar will be? All that's observable is the open. Therefore if your system is based on trading charts or bars as it where and you entered based on some condition met during that bar that no longer was met when the bar has closed, you may find yourself wondering what to do.
The solution? If you want to trade based on bars, only consider what's observable at any given time...the open of the current bar, data from past bars. If you want to trade based on conditions such as "as soon as the ask touches X" you'll likely want tick data.