I can give you an example of when I have sold on an upswing on a loser stock, in the process accepting a loss. I believe this is what you are referring to below with your statement:
(your capital Gain calculations on a LOSS post [LOL]
Well I used this to perfection March/April in the case of AirIQ (IQ), which trades on the Venture exchange here, or maybe it is the TSX. Check out the illuminating chart below:
I got out of a situation where I was down several thousand dollars and accepted a $300 loss. Not bad.. I would say.. The thing went up on some news that had no LR impact, I sold the damn thing and moved on. It is a good strategy. Look where it is now...