Complications - a doctor's life would be so much easier without them, and they happen with statistical regularity to anyone who has surgery. Infections, bruising, fluid collections, imperfect results, slow healing, and other irritating complications are just unavoidable in a few patients. Doing surgery isn't like changing the oil in a car. People all heal differently and surgery can be done in many different ways. A doctor who claims that he never has problems with his patients is either inexperienced or a liar.
Cosmetic surgery is often a trade-off between good results and potential for problems.
Read this last sentence again. It is a key concept. In other words, your chance for the best possible result may be related to how much surgery you have, and with more surgery, there is more chance of a problem. For example, with a face peel, the chance of scarring and the removal of wrinkles is increased with deeper peeling. The doctor has to judge just where to stop.