As I reflect on my past experiences, I'm not so sure that I can 100% agree with the saying. When I think about areas in my past where I consider myself to have been successful, for none of them did I have a plan. If I was lacking a plan, then how was I able to succeed? What is luck, like winning the lottery, or is planning an optional part of being successful?
For the areas that I was successful, I did have a sense of my goal and I took regular action towards the goal. Sometimes massive action and other times small action, though it was regular action. I also spent much time reading information about my goal and talking to others about my goal to get ideas about how it can be achieved. I was also open to try all sorts of different things to achieve the goal.
Maybe planning is just another type of action, that has various levels of usefulness, depending on the person and what they are trying to achieve. This also reminds me the saying by Carl von Clausewitz "No campaign plan survives first contact with the enemy." When making plans, it is not so important if we actually end up following this exact plan. The process of planning will help our brain to think about different options and what we might do when things don't go the way we want.
So, I am removing planning as a critical step for success. Instead, I am going to add "Review". Meaning that after you have set a goal and taken some action you should take the time to review your goals and action and see how is it working out for you. If you think there should be adjustments then make them.