You are correct, but let's not also forget that keeping that decision alive is based on the investors finance status. If it's the type that doesn't have much and is just managing based on earnings, if that earnings is cut short, there is a higher chance that they will, first of all, stop their regular accumulation process, and if there is a need for money to be used, it might also be tempered with. In such a situation, it's not about being determined; it's about making use of the only available resources. Sometimes this is what happens to some investors that make it look as if they don't hold onto their own decision.
You make good point. Investor ability to stick with their plans can be greatly affected by their financial situation. When investors depend on regular income to pay for their investments problem with that income can make them rethink their priorities. In these situations it is not that they lack determination but rather they are being practical because they do not have a lot of money. This shows how important it is to have strong financial base to support long term investment plans.