According to psychological research, written goals are much more powerful than unwritten ones. I think by writing down goals we start to anticipate how we will achieve those goals and start to build our way power as our brains just does not have enough working memory to do all that without committing the goals to paper.
There are three types of goals: process goals, performance goals and outcome goals. As a former athlete, I think process goals are the most valuable since practising reaching a process goal is demanding and if you fail, it will not be as public as failing to achieve an outcome goal.
“Plans are irrelevant; planning is everything. ”