During the 2022 market decline, you've probably seen advice to the effect of "don't sell your stocks just because they're down." And that's a great principle to incorporate into a long-term investment strategy.

But what happens when it's more than just a price decline? What happens when a stock's price drops and the company fails to do what you had hoped when you bought it?

A busted investment thesis can certainly be a good reason to cut your losses and sell, and I've done it a few times when things haven't worked out. However, like most investing concepts, it's not a one-size-fits-all reason to hit the sell button.

In fact, two positions in my portfolio that went public during the special purpose acquisition company (SPAC) boom are in this category. Their businesses didn't quite live up to initial expectations, but I'm keeping them anyway. And here's why.

First, in full disclosure, both are rather small positions for me. Combined, they make up about 1% of my investment portfolio. But I haven't sold them and don't plan to.

A few bumps in the road

Arguably the most significant SPAC initial public offering (IPO) of all time, electric-vehicle start-up Lucid Group (LCID -2.86%) had some pretty high expectations from investors. The company's Lucid Air sedan recently won Motor Trend's Car of the Year honors and was widely considered to be the most realistic competitive threat to Tesla. To be fair, many still believe that.

However, to say that Lucid hasn't met its initial expectations would be an understatement. In a presentation (before combining with a SPAC sponsored by Churchill Capital), Lucid anticipated making 20,000 deliveries in 2022. It won't get there. As of the company's recent guidance, it's on track to deliver 6,000 to 7,000 cars this year.

In that same presentation, Lucid projected a run-rate production of 500,000 units by 2030, which would translate into a 4% share of the market. And I take that with a big grain of salt at this point. But I'm holding on to my Lucid shares for a few reasons.

Missing production targets isn't completely Lucid's fault. Supply chain constraints from its parts suppliers are largely to blame for the miss. It isn't due to a lack of customer demand, and the product quality is fantastic. For Lucid to produce 500,000 cars annually by the end of the decade seems a bit of a stretch, but I still see a very bright future for the company.

A genetics leader with a big advantage

There are few investors I respect more than Richard Branson, so when a blank-check company sponsored by his Virgin Group took genetics company 23andMe (ME -4.66%) public, I took a closer look.

The thesis sounds great. 23andMe has more genotyped individuals than any other company in the world -- and by a wide margin. It can generate revenue from its consumer genetics business while using its massive amount of data to develop pharmaceuticals. And as any experienced pharmaceutical investor can tell you, even one successful therapeutic can be worth billions.

At the time the SPAC merger was announced, 23andMe was projecting $256 million in revenue in its 2022 fiscal year and a 51% gross margin. While it actually exceeded that, the company's margins weren't quite as strong as hoped for, and it lost $217 million in that time period. Plus, recent revenue growth has been sluggish, at just 9% year over year in the quarter ending in June.

I'm holding on to my small position, however, as the pharmaceutical program has largely been doing what I had hoped. There is a pipeline of over 50 different development programs, including two candidate in Phase 1 trials. 23andMe has a market cap of just $1.3 billion and more than $479 million in net cash on the balance sheet, so the reward potential is pretty high if the pharmaceutical side is successful and the company can get its cash burn under control.

Know what you're getting into

Both of these are rather small investments in my portfolio, and I plan to keep it that way. Both could be absolute home runs if things go well, but they could also go down a lot more (even to zero) if they can't execute on their visions. I'm prepared for a bit of a roller-coaster ride with this speculative part of my portfolio and suggest that, if you consider buying them, you prepare for the same.