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Unfortunately, the answer isn't as straightforward as one might think. Choosing to sell a holding really depends on each individual's financial situation and investment goals. Case in point, I own Canadian Tire (have for a couple of years). I bought it as part of my dividend growth portfolio as it had an impressive streak of raising dividends. I am holding it because, it has maintained its streak and is doing better than expected during this pandemic. I had my finger on the sell button earlier this fall, but after it delivers pretty solid results and raised the dividend again - i held off.
That being said, I continue to watch it closely and may eventually dispose of my position. If however, I had bought the company has a growth stock - at this point I might be looking more seriously at selling. The company is only expected to grow earnings and revenue by 2.5% annually (using 2019 end numbers) through the end of 2021. In other words, the pandemic has impacted the economy and the company's once high growth rate has slowed considerably. Not that it's a bad stock, but if my investment thesis was to see double-digit growth - then I'd likely move on.
At current valuations, 12 times forward earnings and 0.78 times sales - Canadian Tire actually isn't that expensive. I would not say its cheap either but close to fairly valued. Given this, I'd expect slow and stead growth assuming a rebounding economy. Any major lockdown, or further setbacks during this pandemic however, and the stock can very much crash again.
Of note, there is also nothing wrong with booking gains as well. Maybe you see another (and more lucrative) investment opportunity that fits your investment goals. Maybe you need the money. The important thing is what works for you. Typically, this involves going back to your original investment thesis - why did you buy it in the first place? If that has changed in any meaningful way (for the worse), then perhaps it may be time to move or lighten your position.
So many factors that go into such a decision. Just don't let emotion guide you - let the numbers do the talking.
Mat