If we assume the numbers in the plot, then your expected profit from this strategy is:

0.8*70-0.2*430 = -30

however, if you manage to cut your losses at

-0.8*70/0.2 = -280

the strategy breaks even.

Thus, I'd add that one needs to be confident that one can keep up 80% win rate AND cutting losses at maximally 280, in order to make non-negative profit (neglecting fees). Cutting losses quicker will result in a lower win rate (as there might be trades that first go down and then later might have gone up after being cut).