I try my hardest not do. My cost basis has nothing to do with whether the stock is currently a good investment or not (except of course for tax planning purposes). A stock where you are playing with "house money" is no more or less risky than one where you have a loss or are even. The only difference is emotional.
I don’t actually think that way about any current position, whether biotech or otherwise; I was merely replying to Dave’s question about whether I was “riding on house money.”