Here's something to consider: Even in the very best organizations, almost every manager will have to deal with at least one problem employee - uncooperative, emotionally unstable, chronically late, "just getting by" performance, etc. - each year. It may not make it easier, but you are not alone when it comes to the uncomfortable task of addressing performance problems.
Falling stars represent only a small percent of any team. Yet some managers spend a great deal of their time with people in this group. That means that the super stars and middle stars are not receiving the valuable coaching and other forms of attention from you that they need. And spending so much time dealing with performance problems doesn't do a whole lot for the coach's job satisfaction either.
Sometimes when a team member consistently underperforms, the manager assumes that he or she has failed as a coach. That's not necessarily true. A good coach helps employees get to where they need to be. But, ultimately, it's each employee's responsibility to decide whether to be a super star, a middle star, or a falling star. Truth is, you can influence that decision but you can't control it.
If you have established a positive work climate, you have a decision to make with each problem. You can close your eyes, live with the situation, and accept the negative impact of your falling stars' lower performance. Or, you can conduct a performance improvement session in which the employee will either commit to your standards - or choose to ignore the problem and face the logical consequences.