This statement is somewhat overgeneral in that there are many normal jobs that require as much preparation or more as being a patrol officer does. However, it is possible to argue that this job requires more preparation than many jobs do.
We should, first of all, realize that there are many jobs that require both emotional and technical preparation. An emergency room doctor or even a surgeon, for example, must be prepared to do various sorts of medical procedures while under stress. A teacher must plan out lessons while being emotionally prepared for all sorts of behaviors that students can exhibit and which must be dealt with. These are “normal” jobs that require a great deal of preparation.
Being a patrol officer is similar to these jobs. A patrol officer must be prepared in both technical and psychological/emotional ways. The officer must know all the details of how to do his or her job. The officer must be prepared to do things like securing a crime scene or providing emergency first aid. These are things for which the officer needs knowledge. The officer also needs to be mentally and emotionally prepared for anything. Any shift could bring the officer into contact with extremely violent people or with terrible tragedies. Alternatively, a shift could simply be boring and routine. The officer must be prepared for either of these.
Thus, the job of a police officer does require a great deal of preparation. It requires more preparation than many jobs, but it does not require more than every “normal” job out there.