One use of your personal book of knowledge (PBOK) is to increase your efficiency to increase your productivity.
This is accomplished by documenting your process for doing things before you do them. Having your process documented allows you to examine and refine the process. When you carry out the process you again learn more about the process to refine the process more.
Ideally, you have a process for everything you do and then the overall process becomes:
1. Refine and document the process
2. Execute the process
3. Reflect on how well the process went
With this process, every time you carry out the process there is the opportunity for the process to be improved.