Studies show that once you injure a certain body part you have a higher chance of re-injuring it down the road, even if you have managed to overcome your issue with surgery or therapy. This is partly due to people returning to whatever activity led to the original problem, but also because each of our body types make us prone to certain issues and that sometimes after an injury we don't heal 100%.
All of which is why you should keep up with your physical therapy exercises even after you feel like you have "healed." As you have probably seen for yourself the exercises and stretches recommended for you during a course of therapy do not only address the specific spot of your problem, but also the surrounding joints and muscles. Some of your therapy might have even addressed more chronic issues like a weak core or poor posture.
When PT patients graduate to our personal training program we make it a point to always incorporate their PT exercises into the routines we design for their overall fitness. Even if you don't have a trainer you should consider doing the same in your own workouts. Not only are those exercises beneficial for you, but since you learned them in physical therapy you know how to execute them with the best form.
As a reminder how-to videos on many basic exercises and stretches can be found in the video section of our website.