This is especially true when dealing with STDs. Many patients stop taking antibiotics for their condition as soon as the condition seems to disappear. Not only is this a risk to themselves, but if can be an infected person appear perfectly normal to a possible sexual partner, leading to the spread of the disease. Worse, if the STD begins to mutate (develop resistance) towards the antibiotic, it could become silent, meaning that it has no immediate symptoms. If you don't finish taking the antibiotic, and the disease builds back up in your system, it will be much harder to diagnose and cure.