3 Rules You Must Remember for Index Investing

I stopped my savings plan because of a market crash. I got tired of saving too much money.
Now that the new NISA has become widespread, I often hear voices like this.
Many people must have started index investing with All Country or S&P 500 funds.
However, there are not a few people who end up quitting because they cannot keep it up.
I wrote this article for those who are about to start, and for those who have started but feel anxious.

Hello. I am Koji, a 20-year-old college student investor. I started NISA at 19, so my investment experience is still just over a year. That is precisely why I share real stories about money for college students from the same perspective, covering both successes and failures.

To conclude, there are three rules you should value in index investing:
・Set a sustainable monthly investment amount
・Do not check your brokerage account too often
・Do not think about timing for taking profits or cutting losses
I will explain them in order.

■ Rule 1: Set a sustainable monthly investment amount

【Are you becoming ‘NISA poor’?】
Recently, the term ‘NISA poor’ has become so widespread that it seems more people are cutting back on their living expenses to put money into NISA.
Of course, I do not want to completely deny the idea of being ‘NISA poor.’ I think it might suit some people’s personalities.
However, for many people, cutting back too much on their daily lives makes the act of investing itself painful.

A savings plan that continues, even with small amounts, is better for long-term investing than one that does not last.
As a result, returns are also more likely to be higher.

【There are times when experiences are more important than investing】
Especially for young people like college students, there are times when you should prioritize experiences over investing.
You can enjoy traveling more while you are still energetic.
You should visit the domestic and international places you have always wanted to go to while you are still a college student.

Going to see friends who live far away.
Spending money on studying for certifications or skill improvement.
These ways of spending money are also more effective when you are young.

That is why it is important to set an investment amount that does not interfere with the money you use for experiences.
I want you to try to set an amount that is sustainable so that you do not sacrifice either ‘protecting your future self’ or ‘enjoying the present.’

■ Rule 2: Do not check your brokerage account management screen too often

【Consider market drops as ‘something that happens’】
If the market is always trending upward, you can check your account without worry.
But if you check it during a downturn, it can become a source of psychological stress.

Even in the last few years, there have been many drops, such as the invasion of Ukraine, Trump’s tariffs, and the situation in Iran.
It is better to consider market drops as something that happens.

【My unrealized gains also dropped significantly】
I myself saw my unrealized gains drop significantly in March 2026 due to the situation in Iran.
At times like that, it is best not to open your brokerage account too much and just not worry about it.

If you make a rule to ‘not look much during market crashes,’ it becomes easier to continue your savings plan.

■ Rule 3: Do not think about timing for taking profits or cutting losses

【’Holding for a long time’ is the foundation of index investing】
In index investing, there is no need to watch the market to buy and sell.
The reason lies in the nature of index investing.

The first reason is that it is likely to be positive when viewed over the long term.
Past data shows that even if there are crashes in the short term, in the long term of 10 or 20 years, indices like the All Country World Equity or S&P 500 have been positive in almost all cases.
In other words, those who stayed in the market longer were more likely to gain profits.

The second reason is that the longer you hold, the more compound interest works in your favor.
The profits earned from your investments will generate even more profits.

【The real time to sell is ‘when you need the money’】
‘If I don’t take profits, isn’t there no point in growing it through investment?’
Some people might think this.

What I do not recommend here is taking profits by saying, ‘The market is up, so let’s lock in some gains.’
So, when is the real time to sell?

That is when you need money for your daily life.
There are times in life when you need large amounts of money, such as for retirement funds, housing, or studying abroad.
That is exactly when you should withdraw money from your brokerage account.

Withdraw money based on your own needs, not market conditions.
This is an important mindset for index investing.

■ Summary

The three rules for continuing index investing are as follows:
・Set a reasonable investment amount and value your current experiences as well
・Do not check your brokerage account too often when the market drops
・Sell based on your life’s timing, not the market’s

Index investing is an investment method that tends to reward those who stick with it.
Rather than aiming for perfection, let’s continue at our own pace for the long term.

Thank you for reading until the end!
Your likes and follows are very encouraging🙏