Trading needs concentration but investment does not need much concentration because you invest certain amount and then you wait until it rise to give you huge profit. Knowledge is necessary for both trading and investment, the rate of success will be more if you have more experience and more understanding about the basics.
More than anything what investors need is to have tough skin, as it is impossible for things to always go our way, and as such an investor will eventually make a mistake and if they are not able to endure it then they will sell for a bad price and lose money, this is exactly what happened to the people that invested near the ATH on 2021 and 2017, and the majority of them were simply unable to keep holding their coins due to their frail mentality.