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Mistakes are to the stock market as volatility is to the chart. Looking back, they are what hurts the most - but also teaches the most. In recent years, I have deliberately tried out many strategies in order to develop my own system. There have been some hits - but also misses, which have shown me what really counts in the long term.

This article is primarily aimed at new investors. I hope to save you from making one or two costly mistakes - or at least to show you what really matters if you want to invest sustainably.

Five examples are particularly influential. They mark the turning points at which I went from being a pure yield hunter to a structured investor.

1. historical performance overvalued

My entry into the $INRG (+1,94 %) (iShares Global Clean Energy ETF) was, in retrospect, almost textbook bad timing. I bought when the story sounded perfect: energy transition, political tailwinds, ESG money, green euphoria. The share price was close to an all-time high and fund providers were outbidding each other with promises for the future.

I let myself be dazzled - not by fundamentals, but by charts and headlines. The ETF portfolio consisted mainly of highly valued solar and hydrogen stocks with P/E ratios that were beyond all reason. I didn't really understand the product and only saw the impressive historical performance.

After a few months, I was down around -17% and realized the loss - a classic example of past performance bias. Today, the ETF is trading significantly lower again.

Learning:

High historical returns are not an argument, but a warning. When a sector is already overrun by institutional money, the regression to the mean begins. Since then, I have checked the composition, valuation levels and the cycle of the narrative for every investment. An ETF is only as good as its components - and hype is no substitute for analysis.

2. value trap instead of value opportunity

$INTC (-0,72 %) (Intel) seemed to me at the time to be a classic underperformance opportunity: lower P/E ratio than $NVDA (+2,84 %) (NVIDIA) or $AMD (+1,91 %) (Advanced Micro Devices), solid cash flow, decent dividend. I saw the numbers, not the structure.

The company has been struggling for years with innovation gaps, manufacturing problems and a protracted strategy. Margins were falling, market share was shrinking - but the valuation looked attractive. This is precisely the nature of a value trap: cheap because the business model is losing competitiveness.

I held on to the thesis for too long and eventually realized a loss of around -21 %. Despite the current upswing, Intel is still lagging behind today, while its competitors have further extended their lead.

Learning:

Valuation alone is not a safety net. Favorable multiples are often a symptom, not an opportunity. I have learned that capital flows, technological dynamics and management quality are crucial. Value only works if the business model is intact - not if you are hoping for a renaissance that is fundamentally unproven.

3. "What falls is cheap" - the fallacy using the example of $PYPL (-1,19 %)
(PayPal)

Another classic mistake: the belief that a sharp fall in the share price is automatically a good entry point. After PayPal's massive correction in 2021, I thought this was a rare opportunity. The company was once overvalued - no question - but I interpreted the setback as a downward exaggeration.

I got in after the share had already fallen sharply and even bought more as it continued to fall. The assumption: "It won't fall that low again." But it continued to fall - and has not recovered sustainably to this day. The exaggerated valuation premium from the boom years was simply no longer justified.

In the end, I realized a loss of around -44 %. The share will probably never reach the old highs again because the market environment, margin structure and growth have changed permanently.

Learning:

A falling share price does not automatically make a share cheap. You have to examine why it has fallen - and whether the fundamental situation has changed. An exaggeration on the upside is often followed by an overcorrection on the downside, and the old valuation remains out of reach for years. Today, I prefer to invest in companies whose trend is intact instead of speculating on "comebacks".

4. warning signals ignored - the example $CLI (-0,43 %)
(Cliq Digital)

For those unfamiliar with CLIQ, the company positions itself as a streaming provider - similar to $NFLX (-1,16 %) (Netflix), only much more niche. On paper, everything seemed to fit: high margins, strong growth, an attractive dividend and a barely noticed small cap with potential.

I saw the opportunities - but not the contradictions. The business model was difficult to understand, the reporting was incomplete and the short interest was extremely high. Nevertheless, I held on to the position - "because the figures were so good".

In the end, I realized a loss of around -26 %, including dividends. Today, the value is almost 90 % lower.

Learning:

If you don't understand a business model, it's not a good idea to be invested. Transparency is not a nice-to-have, but a must. In small caps in particular, you should check carefully whether growth is real, repeatable and sustainable. Since this experience, I have avoided business models that I cannot explain in two sentences - and take high short ratios as a serious warning signal.

5. trend understood - implementation missed

I wanted to focus on the self-service trend early on: Terminals for fast food chains, supermarkets, airports. A massive growth market - but I was looking for the wrong player. I found $M3BK (-1,42 %) (Pyramid), a small German company with a reverse IPO structure, hardly any investor relations, low liquidity and a non-transparent balance sheet.

I invested, convinced by the trend - not the business model. The share fell for months and I realized a loss of around -34%. Today it is trading at penny stock level.

Learning:

A strong trend alone does not make a good investment. The decisive factor is who has the real leverage in the value chain. It is often not the visible brands that benefit, but the blade manufacturers in the background - suppliers, infrastructure companies, platform providers. I have learned to analyze the ecosystem first and then look for the most profitable position in it.

Overarching learnings

These five mistakes were expensive, but their impact was priceless. Today, they are an integral part of my methodology - both in the 10B model (for growth opportunities) and in the Hidden Quality Radar (for quality values).

1. foundation beats narrative:

Stories are loud, but numbers are honest. Today, I check every investment for cash flow quality, return on capital and strategic positioning - and only then for valuation.

2. timing is crucial - but only in the right context:

I used to think that timing was unimportant, the main thing was to invest for the long term. Today I have a more differentiated view: the time of entry is a decisive factor in determining the risk/reward profile. If you buy in euphoric phases, you often pay for the correction years later. On the other hand, those who invest in downward exaggerations - with fundamental analysis and patience - gain a massive advantage. Timing is therefore not a game of chance, but the result of preparation, market observation and discipline.

3. accept small losses:

Discipline beats hope. Getting out early when things go wrong saves capital for better opportunities.

Here I would like to recommend a great article by @DonkeyInvestor recommend: https://getqu.in/eymPwi/

4 Transparency and management count:

I only invest in companies whose strategy and communication are transparent. Trust is not a gut feeling, but a data point.

These experiences have shaped the way I think today: patience instead of greed, quality before valuation, understanding before actionism. I have learned that you don't always have to be right on the stock market - you should think consistently.

Mistakes are inevitable. But if you reflect on them honestly, you build up your expertise with every bad experience.

What mistakes have shaped you - and what have you learned from them?