Then you should celebrate! Because it means you've helped create a better human being. Whatever that is for your activity, full 'graduation' could mean different things to different people.
You could use your belt grade as a 'graduated' approach to assessment. Meaning that based on what your metric is at which belt, it has different weight. This of course does not fair well for our existing reports, but we'll work on that for a future release.
At a minimum however, if your student/client 'graduates' then you've taken them through that tough few years that most typically fail. Your goal has been accomplished. Congratulations.