As I approach my two-year anniversary of writing for the Fool, I thought it would be interesting to go back and look at all of the bullish calls I made in 2019. In sorting the data, I assumed readers of my articles bought the shares in question at the open of the next trading day. Of course, in real life nobody did that (not even me). But if you had invested an equal dollar amount in every stock I suggested, overall you would have quadrupled your money.

While I'm happy, and I hope you're happy, several of my stocks have underperformed the market, and nine have lost money for shareholders -- so that's humbling. I was wrong multiple times, and I will probably be wrong multiple times this year, too. Sometimes my crystal ball is on the fritz. Anyway, let's dive in and see how I did. 

A person rides a bike to the top of a mountain.

Image Source: Getty Images. 

1. First, some numbers

Here are all of my bullish calls in 2019, and how the stocks performed from the time of the hypothetical purchase through Aug. 9, 2021. 

Stock Number of Articles Stock Price on the First Trading Day After Article Was Published in 2019 Stock Price at the End of Trading on August 9, 2021 Percentage Gain
Afterpay 2

$20.00 and $20.55

$99.02 388%
Altus Midstream 1 $49.60 $66.13 33%
Amarin 4

$21.82, $20.65, $20.70, and $14.32

$4.85 (74%)
Apple 2

$71.17 and $67.50 

$146.09 111%
Arrowhead Pharmaceuticals 1 $49.39 $62.78 27%
Autodesk 1 $179.31 $332.77 85%
Blue Prism 1 $13.17 $11.62 (12%)
Blueprint Medicines 1 $77.38 $94.50 22%
BridgeBio Pharma 1 $24.83 $53.39 115%
Carvana 1 $67.28 $356.34 430%
CrowdStrike 1 $47.25 $263.56 458%
Datadog 3 $37.30, $32.64, and $36.00 $130 269%
Denali Therapeutics 1 $15.35 $53.49 248%
Disney 1 $147.14 $176.72 20%
Enphase Energy  1 $19.97 $185.56 829%
Farfetch 3 $9.56, $8.38, and $8.82 $47.22 431%
InMode  1 $44.01 $114.26 160%
Innovative Industrial Properties 1 $91.45 $227.86 149%
Ionis Pharmaceuticals 1 $56.27 $38.56 (31%)
Iovance Biotherapeutics 1 $23.66 $24.24 2%
Malibu Boats 2 $39.32 and $38.13 $81.66 111%
MeiraGTx 2 $15.01 and $18.81 $14.71 (12%)
Mirati Therapeutics  1 $104.59 $148.21 42%
MongoDB 2 $139.92 and $117.57 $380.38 206%
Novavax (NASDAQ:NVAX) 2 $4.46 and $4.00 $213.13 4,954%
Personalis 1 $10.40 $20.78 100%
RegenXbio  1 $39.96 $32.50 (19%)
SciPlay 1 $9.46 $17.31 83%
Sea  1 $37.08 $307.14 728%
Shopify 2 $402.76 and $336.00 $1,549.99 327%
SmartSheet 2 $43.93 and $40.49 $71.96 71%
SmileDirectClub  3 $8.05, $11.78, and $13.04 $6.70 (36%)
Solaris Oilfield 1 $12.51 $7.87 (37%)
Square  1 $63.20 $279.73 343%
StoneCo  1 $41.06 $58.15 42%
Ubiquiti  1 $193.75 $310.28 60%
Ubisoft  1 $11.92 $11.80 (1%)
Veeva Systems  1 $148.61 $332.34 124%
Vir Bio 1 $13.80 $40.10 190%
Virgin Galactic  1 $7.33 $35.21 380%
W&T Offshore  1 $4.74 $3.12 (34%)
Zillow  2 $41.15 and $30.13 $101.69 192%
Zoom Video  1 $66.50 $383.34 476%

Data from Yahoo Finance.

If you count all those up, it's 61 bullish calls. The final two are Immunomedics and Glu Mobile. Both companies have been acquired, so they don't exist anymore. Immunomedics in particular had a nice run, jumping from $16 at the time of my article to $88 one year later. But neither stock exists now, so I'm excluding those numbers.

What we're left with is 61 bullish calls on 43 stocks. And what are the lessons we might learn?

2. Let your winners run

Of course my Novavax calls on Nov. 2 and Nov. 26 had a massive effect on my returns. At the time, shares were going for $4 and pennies. Now Novavax is trading for $213 a share. Obviously in 2019 I had no idea that COVID-19 was about to hit, or that all the vaccine stocks would soon skyrocket.

If you sold Novavax after a double or a triple or a quadruple, that means you sold at $8 a share, or $12 a share, or $16 a share. Think about this for a second. This whole hypothetical port is up 319%, a quadruple in two years. That's an excellent return. But you only get that excellent return if you hold your Novavax shares for the full 4,954% return. 

3. Diversify!

One of the ironies of my 2019 performance was that my most bullish stock pick (by number of articles written) was Amarin -- but Amarin was my worst performer by far, losing 74% of its value. In my hypothetical portfolio, I invested twice as much in Amarin (four articles = $4,000) as Novavax (two articles = $2,000). In real life, I invested more in Amarin, too. I had more faith in Amarin. I felt it was a sure thing while Novavax was a risky micro cap. 

Overall, I had 11 stock picks do better than my 319% overall return: Afterpay, Carvana, CrowdStrike, Enphase, Farfetch, Novavax, Sea, Shopify, Square, Virgin Galactic, and Zoom Video. That means the other 50 stocks were actually dragging down my returns. And of course it's not easy for a stock to quadruple in two years. Shopify, my favorite stock, barely did it (up 327%). Ditto with Square, my second favorite stock (up 342%).

It might be a good idea to look at your portfolio and ask yourself whether any of your stocks can go up 10,000% from these levels. If none of your stocks can go that high, you might be risking underperformance. It's really nice -- and sometimes, financially rewarding -- to invest small amounts in high-risk companies with significant upside.   

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.