Oscar Bonilla, PhD
As an instructor, the hardest part isn't teaching what works. It's watching a capable, hardworking student with all the right intentions lose money due to a preventable mistake. I've seen this scene play out many times, and over time, I noticed something encouraging: the mistakes that cost students the most are almost always the same. And what repeats can be anticipated.
These are the stumbles that, time and again, have cost beginners the most money. I'm not telling you this to scare you, but so you can see them coming before they hit you.
Wanting quick results and abandoning the process
This is, by far, the most expensive one. The student arrives in a hurry, expecting to get rich in a few months, and when results don't arrive at the speed they imagined, they give up just as the work was about to pay off.
There is a story Napoleon Hill tells in Think and Grow Rich that sums this up perfectly. A man bought a mine during the gold rush, dug and dug, and when he found nothing, he gave up and sold his equipment for pennies. The man who bought the mine called an expert, dug just one more meter in the same spot, and found one of the largest gold veins in the area. The first man quit one meter from the treasure. It's the same with money: many people leave the process one step from the result, convinced that "this isn't for them," when all they lacked was consistency. That's why I insist so much on trusting the process.
Risking money they couldn't afford to lose
The second most costly mistake is putting money into the market that was needed for living expenses. Students who invested emergency savings, or worse, borrowed money, looking to multiply it quickly.
The problem isn't just financial; it's emotional. When you risk money you can't afford to lose, fear takes over every decision, and fear is a terrible advisor. You end up selling at the worst possible time, with no patience to wait, because that money never should have been there in the first place. The lesson is harsh but clear: only money you can let work without its loss destabilizing your life should enter the market.
Investing without education, guided by others
Many of the most expensive blows came from acting on outside advice. They bought something because an acquaintance, a video, or a supposed expert said it would go up, without understanding themselves what they were doing or why.
When the trade went wrong—and it often did—the person who gave the advice wasn't there to answer for it. The student was left alone with the loss and without understanding what had happened, because they never understood the decision in the first place. Learning takes time, yes, but it always costs less than the bill for trading blindly while relying on others.
Letting fear make the decisions
And the fourth, the most human of all: selling in a panic during downturns. Every time the market corrected sharply, a group of students sold out of fear, turning a temporary dip into a permanent loss, and often later watched the market recover without them in it.
It wasn't the market that took their money. It was their reaction. The lesson those who overcame it learned was to stop staring at the screen constantly, trust their plan, and remember that downturns are a normal part of the journey, not the end of the world. If this is your weak spot, here is how to control your emotions when investing.
If you look at these four mistakes together, none of them are a problem of intelligence or bad luck. They are impatience, excessive risk, lack of education, and uncontrolled fear. And that is the best possible news, because all four can be prevented with education, method, and discipline. The student who knows them in advance has a huge advantage over the one who discovers them by paying for them.
The question I leave you with is this: of these four mistakes, which one would you be most likely to make, given your personality? Knowing your own weakness is the first step to ensuring it doesn't cost you what it cost others. Keep learning to invest with a clear head alongside Oscar Bonilla. Financial freedom for you is possible, and it starts by learning from the mistakes others have already paid for, so you don't repeat them.
