In 2011, I bought Grainger (GWW), a great stock that went down with the market during the summer. I did what I rarely managed to do: spot and buy a great company that went down a lot with the market for no reason. A few months later, Grainger was up like 25% and I sold it. I don't exactly remember why. I think that growth didn't look as good for the future. Or maybe I found some shitty penny stock to replace it (it was my "penny stock" period).
Recently, I took another look at the stock and I realized that it went from about 200$ in february 2012 (when I sold it) to about 600$ these days.
I could have tripled my money over these last 11 years but no, I tried to find something else more exciting.
What's crazy is that Grainger is still not that expensive even if it's track record has been great. The only thing that's changed is the debt level which is higher than before, but not so worrying. Of course, interest rates are way higher than before now. So, that's a bit of a concern but everything else looks great in my opinion.
Anyway, It's another of those cases of companies that looked good 10 years ago and that should never have been sold. Like Mastercard. Like O'Reilly. Like some of the shares of Constellation Software that I sold many years ago.
I came back to all of them and I paid more than what I initially paid.
When it's a very good company, don't sell it except if things look very bad. By very bad, I mean something illegal or some serious shit. Not a momentary stop of growth.