There are times and places where you will not be able to carry around your pocket knife, but they will vary tremendously. In some countries, carrying knives in public is forbidden. But, often times there is an exception for pocket knives; it just depends on the jurisdiction. However, in certain events or places (at a school, in a courthouse, through public buildings, at a public event) they may be prohibited with no exceptions.
If you are ever nervous about going to an event with a pocket knife, conduct some research to find out if they will allow it. If you have to, you could even call ahead to make sure. Unless you are going to school or to a governmental building, most of the time you should be safe to carry it with you, though.