Design your life. Not only should you have clear and definite goals, but also you should have definite plans to get to them as well. Definiteness of purpose and definiteness of how to achieve those goals and purposes are both essential.
Write those plans down somewhere. That is the only way your mind will take those plans seriously. That is the only way your mind will move these items from the wishes and dreams zone to the serious intentions zone.
Also you will forget the information if you don’t write it down, and if you don’t forget it, then this means that you’re carrying or holding the information, goals, or plans in your mind or brain all the time. That takes up space from your working memory and short-term memory. That also exhausts you and makes you tired all the time. Also writing things down organizes things in your mind in a spacial way and exercises your inhibitory centers.