It's easy to invest.
It's harder to hodl properly.
The hardest thing is to avoid greed. Like suppose someone bought bitcoin at $10000 and now price is $20000 in one year. What investment option could offer 100% return in one year ? It is impossible for majority not to sell at this moment. This will think that I should book profits now. That is why it is not easy to hold bitcoin for long duration like 5-10 years.