1 Stocks and Shares ISA mistake that will make me a better investor in 2026
My Stocks and Shares ISA has underperformed this year so Iâve been looking at why. And while some things are out of my control, there’s one mistake that stands out to me.
Hindsight is always 20/20, but one of my portfolio moves has turned out to be a mistake that I could have avoided. The good news is that I think I can avoid a repeat in 2026.
Selling too soon
The mistake was selling my Citigroup (NYSE:C) shares. Exiting investments too soon has been an ongoing weakness in my investing and itâs one Iâve been working to get better at.
It doesnât matter how good my investment ideas are, Iâm not going to benefit if I sell too soon. Itâs a bit like Noah building the ark but selling it to someone else just as it started raining!
Anyway, back to Citigroup. Jane Fraserâs plan to simplify the company by selling its operations in countries where it canât establish a meaningful presence has been a very good one.
As a result, the stock trades at a higher price-to-book (P/B) ratio (which I predicted) and the company is buying back shares (which I also predicted). But none of that is much use to me.
My investment in Citigroup wasnât a total disaster, by any means. I made a solid enough profit, but I sold my entire stake at around $85 in June and the stock is now trading at $111.
Thatâs a 30% gain in six months I missed out on. And while I sold because the stock had reached my estimate of its intrinsic value, itâs fair to say I made a mistake in moving on.
Lesson learned
Fast forward to today and I find myself in a similar position with a different stock. The Games Workshop (LSE:GAW) share price has doubled since I started buying shares in the company.
As a result, the price-to-earnings (P/E) ratio has gone up and the dividend yield has gone down. And I think buying the stock today is a much less attractive proposition as a result.
The pre-2026 version of me might have sold my shares to take advantage of some more obvious-looking bargains. But the effect of selling too early some of my ISA holdings this year is still very much front of mind.
In some ways, itâs easier with Games Workshop. Itâs a company that I think has strong long-term growth prospects, rather than an underperforming firm with a lot of potential.
Thatâs not to say the stock is guaranteed to do well in 2026. Despite strong revenue growth in its core operations, the effects of inflation and US tariffs are starting to show up on margins.
This is a risk going forward. But while Iâm not adding to my investment at todayâs prices, the firmâs strong intellectual property is enough to convince me not to sell.
Warren Buffett
Warren Buffett once said that the stock market is a device for transferring money from the patient to the impatient. That was certainly the case for my Citigroup investment.
Fortunately for me, it shouldnât be that difficult to do better going forward. And thatâs what Iâll be aiming to do with my Stocks and Shares ISA in 2026.
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Citigroup is an advertising partner of Motley Fool Money. Stephen Wright has positions in Games Workshop Group Plc. The Motley Fool UK has recommended Games Workshop Group Plc. Views expressed on the companies mentioned in this article are those of the writer and therefore may differ from the official recommendations we make in our subscription services such as Share Advisor, Hidden Winners and Pro. Here at The Motley Fool we believe that considering a diverse range of insights makes us better investors.
