Investing: Tell Me Why (I Hate Mondays)

Chronicling a new experiment, seeking the financial freedom to live the writer's life.

I’m quietly chronicling my experiment with a stock picking method I developed. IT had good results for 2.5 weeks before, but that might have been chance. Today was the first open market day while journaling, and it didn’t go well.

Today continued Friday’s dramatic drop in the market as investors unleashed their fears that AI profits will be delayed more than promised.

My stocks in the method lost a total of $681.28, today, or -1.6%. The S&P is down 0.16%, and no, that’s not a great start.

There are a few reasons for this that are actionable. First, I’d determined which stocks to sell using (for the first time) the method’s data itself rather than just a set time frame. Unfortunately, I thought the market would be rebounding today. The method didn’t tell me that; it was my assumption, and based on that assumption, I made the choice to sell at the end of the day. What that did was cause me to lose more. I will sell early from now on.

Second, my big gainers were having big sell offs, so I lost big. Hopefully, a refined selling process can avoid this in the future.

Third, Mondays are a problem that I don’t know how to fix. The data I use tracks market psychology and temperaments have a chance to cool and minds a chance to change after the market’s been closed for two days. I will track the method’s picks for Mondays and will continue to sell on Mondays, but I will probably stop buying unless the data proves that I shouldn’t be all Garfield (or Bob Geldoff) about Mondays.

Method -1.6%; S&P -0.16%

Wednesday stocks: -4.9%
Thursday: 0.26%
Friday: 0.34%
Monday: -3.28%

I only thought to add the daily totals the next morning, by which time Tuesday had been replaced. The numbers above reflect how stocks on each particular day of purchase fared today. Tuesday and Wednesday were both hurt by losses of gains made in Rocket Lab. I discuss the issues with Monday above.

My Buys and Sells for Tuesday, 12/16/2025.

Buys:
F (Ford) price dropped between after hours and pre-market
FUTU (Futu Holdings ADR) price dropped
LLY (Eli Lilly) price rose significantly
PG (Procter & Gamble) price rose
BMY (Bristol Myers Squibb) price unchanged
NTRA (Natera) price rose
GLD (SPDR Gold Shares) price dropped significantly
SIL (Global X Silver Miners ETF) price dropped significantly
TIGO (Millicom International) price rose

I’ll purchase all the buy stock, regardless of the price changes noted, but I include the notes in case they prove meaningful to the data. So far, the evidence suggests otherwise.

Sells:
LITE (Lumentum Holdings)
NEM (Newmont)
RIVN (Rivian Automotive)
BRKB (Berkshire Hathaway)
ANET (Arista Networks)
AG (First Magestic Silver)
CSCO (Cisco Systems)
TMUS (T Mobile US)
NKE (Nike)
WAB (Westinghouse Air Brakes Technologies)
GS (Goldman Sachs)
FDX (Fedex)
HD (Home Depot)
CNC (Centene)
AAPL (Apple)
AXON (Axon Enterprise)
MU (Micron Technology)
SMR (Nuscale Power)

Notes: There are more buys than I expected, and I don’t know if that bodes well for tomorrow or simply means that I’ve improved the quality of my watch lists. My experience so far has been that the better the day, the more stocks are picked up by my method. (Eventually, that becomes a problem.) If this isn’t entirely reflecting a better stock selection to choose from, it may signal a psychologically positive shift in the mark.

There are a large number of sells because a) I still own a large number of stocks from the previous week, and b) I’ve tightened the requirement for a stock to stay. Even so, I think the only stock that gave me pause was AG (First Majestic Silver).

Tuesday edit: A glance at some of the sell stocks show significant price drops between overnight and pre-market. With a selling system in price last week, most or all of these continued losses might have been avoided. If so, I hope to see a positive impact on gains starting Wednesday.

My plan for Tuesday is to sell stocks late in the pre-market. I’ll move buying from 9:30am to 10am. When I was initially testing the data on which I’m making my purchases, I was buying and selling the same day. Fighting the early volatility often improved my margins because stocks were rising. I’m now holding stocks overnight (at the very least) and with this change will test avoiding the early volatility.

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Disclaimer: The information provided in this material is for educational and informational purposes only and should not be construed as financial advice. I am not a licensed financial advisor, and nothing contained herein constitutes a recommendation to buy, sell, or hold any security or investment. Investing in stocks involves risk, including the potential loss of principal. Before making any investment decisions, you should conduct your own research and consult with a qualified financial professional who can assess your individual circumstances, financial situation, and investment objectives.

— Thaddeus Thomas