It is investors attitude toward a project that will ensure a good or bad returns. The ability of investors to value a token either holding them for a long term or offsetting them early is a major cause in how a coin behave.
Yes the investment decision is very important in determining the fate of your crypto journey. If you invest in the right coin, you would be able to get good returns in future and this motivates you more and more to reinvest. However if you make a mistake, it usually discourage you and can lead to loss. This is why it is suggested to have good knowledge about something before investing your money in it.