There are several reasons for this. Every sale can increase costs, trigger taxes, and tempt you to make decisions based on emotion. On top of that, market movements are extremely hard to predict consistently. That is why a long-term, disciplined approach is usually the more sensible option for ordinary investors.
Why this matters for everyday investors
If you are investing for the future — whether that means building wealth, saving for a home, creating financial security, or preparing for retirement — the most important thing is usually not finding the perfect moment to buy or sell. What matters far more is staying invested for long enough.
A very common mistake happens when markets fall sharply and the headlines turn negative. That is often when people sell their investments just to feel safer. In the moment, that decision may feel like relief. In reality, it can mean turning a temporary decline into a permanent loss just before the market begins to recover. One of the biggest advantages of long-term investing is that you do not need to react to every swing in the market.
Time is an investor’s greatest ally
The real power of investing comes from time. When an investment is left alone for years, returns start to build not only on the original capital but also on the gains that have already accumulated. This is the compounding effect.
At first, the difference may look small. Over time, though, it becomes significant. That is why investing success usually depends less on perfect timing and more on staying in the market long enough. For many people, this is the hardest part, because doing nothing can feel passive. In reality, it is often a form of discipline.
Why frequent buying and selling tends to hurt returns
Active trading becomes especially tempting when markets are volatile. The idea is understandable: sell before things get worse, then buy back in once the recovery begins. The problem is that very few people can do this well on a consistent basis.
In practice, investors often sell only after prices have already fallen and return only after the recovery is already well underway. On top of that, every unnecessary move can increase transaction costs and create tax consequences. In many European countries, capital gains are typically taxed when you sell an investment at a profit rather than while you continue holding it, so selling along the way can reduce the amount of money that remains invested and compounding.
Example: how taxes can reduce long-term returns
Imagine two investors who both start with €10,000. For simplicity, let’s assume the investment earns an average return of 7% per year. This is only an illustration, not a promise of future returns.
The first investor stays invested for 20 years without selling. In that case, the original €10,000 grows to about €38,700.
The second investor follows the same path, but sells after 10 years. By that point, the investment would be worth about €19,700, meaning the gain is roughly €9,700. If a capital gains tax of 30% is applied to that profit, about €2,900 goes to tax, leaving roughly €16,800 to reinvest.
If that remaining amount is then invested again for the next 10 years at the same assumed return, the final value comes to about €33,000.
The difference is more than €5,000, even though both investors received the same market return. The key difference is that one investor triggered taxes halfway through the journey and lost part of the compounding effect as a result.
Example: what happens if you miss the market’s best rebound days?
Another major issue with market timing is that the strongest up days often happen very close to the worst down days. Just when the mood feels most negative, the market can suddenly turn.
Take a simple example where a €10,000 investment goes through two bad days followed by two strong recovery days. If the investor stays invested the entire time, the portfolio may recover close to its starting level or even slightly above it. But if the investor sells in panic just before the strongest rebound day, the outcome is much worse.
In this simplified example, the investor who stays invested ends up with about €10,350, while the investor who steps aside at the wrong moment ends up with about €8,280. The gap is more than €2,000.
The example is simplified, but the point is important: market timing is so difficult because the biggest damage often comes from being out of the market at exactly the wrong time. Research and investor education material have repeatedly pointed out that some of the market’s best days tend to occur during bear markets or very close to the beginning of a recovery.
Costs matter more than many people think
Costs are another reason long-term index investing works better for many people. A single trading fee or annual fund charge may look small, but over the years the impact adds up. Every extra euro spent on fees is a euro that can no longer stay invested and grow.
That is why a low-cost, diversified index fund or ETF is often a sensible choice. The simpler the structure of your investing approach, the lower the chance of making expensive mistakes.
Who is this approach best suited for?
Long-term index investing is especially well suited to someone who wants to build wealth over time without spending hours following the market. It also suits people who recognise that emotions can easily interfere with decision-making at exactly the wrong moment.
For many beginners, this is a strong starting point precisely because it does not require constant action. Instead, it relies on a clear plan that can still hold up when the market becomes volatile.
When might selling still make sense?
None of this means investments should never be sold. Selling can be entirely reasonable when you genuinely need the money, when your life situation changes, or when your portfolio no longer matches your goals or risk tolerance. Rebalancing a portfolio or switching from an expensive product to a better one can also be a sensible reason to sell.
The key difference is whether the decision is based on a plan or on fear. Long-term investing is not about refusing to act under any circumstances. It is about avoiding unnecessary decisions driven by emotion rather than judgment.
What should a beginner do in practice?
In many cases, the best solution is surprisingly ordinary. First, it helps to keep an emergency fund separate from your investments so that a market decline does not force you to sell at the wrong time. After that, you can choose a diversified, low-cost index-based investment and automate monthly contributions. Once investing happens automatically, every headline is less likely to disrupt the plan.
It is also helpful to decide in advance when selling would actually be justified. When those rules are set during a calm moment, they are much easier to follow when markets become uncomfortable and emotions start to take over.
Conclusion
For most investors, the best strategy is not constant buying and selling, but a long-term and disciplined approach. When investments are allowed to stay in the market for long enough, costs are kept low, and unnecessary selling is avoided, the chances of benefiting from long-term market growth improve significantly.
Perfect timing is usually not required. What matters much more is having a good enough plan — and being able to stick to it even when the market moves in an uncomfortable direction.