Something investor Jim Slater said which has improved my trading immeasurably, and it sounds obvious, but so often people do not do it(!!!!)
"Cut your losses and run your profits. Never average down".
It's amazing how often people hold onto shares that are loss-making, unwilling to stomach the loss, and watch their capital slowly erode away. In my opinion and experience, 99% of the time, it is best just to cut your loss and invest it elsewhere.
Again with profits, I almost never topslice, as it's like cutting a foot off your race- winning horse. If you are onto a good thing, let the gains run until you either have to sell out, or the story changes.
That's my opinion anyway.
If CNR does blast through 10p, I MAY look at topslicing there, purely because my portfolio will become too heavy in one share, but multi-baggers like this are not exactly common. In most circumstances, the above applies IMO.