It is often difficult to remember after much time has passed why you decided to do what you are now doing. Even if you had written it down in clear detail in a note, that note may have been lost. So it becomes important to trust the decision-making process of your past self.
As an investor, when the market is going through turmoil or your view has become contrarian, you must trust the decision of your past self in order to continue holding your position, as long as your thesis has not been fundamentally broken.
In choosing projects to work on, jobs to take, or relationships to enter into – it is the same. Because you cannot constantly be re-evaluating your “why.” Once you have made a decision you must be focused on the “what” and the “how” entirely, in order to succeed. In every moment you are so focused on the execution of the task, you are trusting that your decision to enter into said task was, and continues to be, a correct one.