Mr. Anderson

It's not that horrible really. Contrary to what some people here say, it is NOT and STD, neither is it a form of herpes. It's a viral infection caused by the Epstein-Barr-virus. The disease is also known as Pfeiffer's disease, after the physician who first described the symptoms.
Therefore, unlike herpes, kissing disease will never come back once you've had it, because your body's adaptive immune system (T- and B-lymphocytes) will recognize the virus when it enters your body.

Symptoms are similar to an influenza infection if im correct, so you'll experience a soar, swollen throat, fever, muscle pains maybe... The main problem is the fatigue, which can last several months, but might be gone within a few weeks. Whatever happens, your body will eventually get rid of it, you'll recover completely and the disease won't return.

The reason it's called kissing disease is because the virus is transmitted by selivary contact (e.g. kissing, but also using the same glass), which is more or less similar to the way herpes-virusses are transmitted. Many youths get it at parties by using the same glass, kissing or coughing/sneezing etc.

Hope this comforts you a little, tell me if you have more questions