LONDON -- One of Warren Buffett's famous investing sayings is "be fearful when others are greedy and greedy only when others are fearful" -- or, in other words, sell when others are buying, and buy when they're selling.

But we might expect Foolish investors to know that, and looking at what Fools have been selling recently might well provide us with some ideas for investments that are past their prime.

So, in this series of articles, we're going to look at what customers of The Motley Fool ShareDealing Service have been selling in the past week or so, and what might have made them decide to do so.

Considerable challenges
Perhaps they saw it coming and decided to sell before the Royal Bank of Scotland (NWG 6.07%) (NWG 6.23%) announced a 6 billion-pound loss in its final results yesterday, since when the share price has fallen over 11%. There was some good news -- operating profit was almost double 2011's figure -- but it clearly wasn't enough to stem the tide of sellers.

Admittedly, anyone who invested in the bank in the past year or so has had a good return -- before the loss-induced drop, its share price was up 24% overall on a year before, and, if you take into account the troughs and peaks in between, put on a substantial 87% between July 2012 and the end of January 2013 for anyone lucky enough to get in and out at the right times (and it would have been luck). But perhaps a lot of people decided not to push their luck until after yesterday's results, and took their profits.

And the bank still faces considerable challenges. Its exposure to liability for mis-sold PPI and interest rate hedging products could yet exceed the already significant provisions it has made. New regulatory requirements for higher capital reserves will inevitably limit the bank's earning potential, and it also has to manage the disposal of anywhere up to £100bn of assets to restore its balance sheet to health. The spectre of the government's eventual sell-off of its 82% stake will always loom large, and, like the other substantially state-owned bank (Lloyds Banking Group), Royal Bank of Scotland still doesn't pay a dividend to shareholders (but does pay big bonuses to its bosses).

A high-quality growth share
Whether you're a seller of Royal Bank of Scotland, or just looking for a high-quality growth share, you'll want to get hold of "The Motley Fool's Top Growth Share For 2013" -- it's the latest report by The Fool's expert analysts and has only just been released.

It's completely free of charge, but like all special reports from TMF it will only be available for a limited period, so get your copy delivered to your inbox now!

*Based on aggregate data from The Motley Fool ShareDealing Service.