It is a rather simple process:
A dispatcher starts the process, assigning an object to one user. The recipient of the task / document can accept or refuse working on that document.
The problem with the personalization step ist, that there ist no way for the recipient to actively refuse working on the task, the only thing for him to do ist not click the "Aufgabe übernehmen" button. The dispatcher on the other hand will never know, if the recipient refused or if he just didn't look into his inbox.
To solve this, the available actions in the users activity are "Refuse" or "Accept". So, if the recipient is not the right one, he has to accept (personalization step) to refuse (activity) - I wouldn't want to explain that to any user.