The tough thing about a person who questions their worth is that they won't tell you about it. You need to guess. Sometimes it's from their silence and other times it is from their over-sensitivity. It is important to let them know that you value them and separate it from the thing they did or said of which you disapprove. These people require a nurturing environment.
At the same time, it doesn't mean that you can't raise complaints with them. However, when you do, you should ensure that you use very specific quantitative language and give them an actionable item. They are very good at delivering when they are told how to serve you. At the same time, you don't want them to be beholden to you. You must ensure that they are looking out for themselves. As opposed to "Do I have discretion?" issue people where you need to make sure your needs and rights are being taken care of, it is the reverse in this case. You need to make sure they are taking care of themselves, else they are very likely to burn themselves out.
|Do I have Discretion?|
|Am I Good?|