My few cents on this.
This is not a very bias to handle. I have already written one post on it. Please check it below
The sunk cost fallacy happens due to a few other biases. Namely Loss Aversion, Endowment Bias & Status Quo Bias.
As I have mentioned the solutions in that post and which I follow very strictly are - KEEP A STRICT STOP-LOSS (it’s up to you to decide the percentage) and NEVER AVERAGE IT DOWN. This means, that if you have substantial conviction in any idea, hold on to it, but NEVER average it down. Once you average it down, the above biases become much more prominent.
I have learnt this after making huge losses by averaging down in both Laurus Labs and Kopran.
dr.vikas