I think any emotion that you don't actively work on can make you sick.
Anger, for example, is an indication that something is not right. You either need to actively do something about the problem, or find a healthy way to come to terms with it and accept it.
Regret can be the same if you dwell on it. At some point, you either make amends, or find a way to accept it. Lingering regret, sadness, remorse... all negative emotions can have an effect on your immune system and make you sick. This has been proven in several studies.