1. A method for operating a hearing aid, comprising the steps of: using a clustering algorithm to find at least one or more hearing environment classes based on feature values in a feature space describing sound situations to which the hearing aid is subjected; activating one or more corresponding parameter sets in a parameter space for said hearing aid according to occurrence of the found classes; in an ongoing learning process, redefining at least one or more of the found classes by at least one of modifying, deleting or merging the one or more found classes dependent on an acoustical environment of a user of the hearing aid, and including continuously analyzing a distribution of said feature values in said feature space and modifying borders of the classes so that one cluster will represent one class; and performing at least one of the following steps selected from the group consisting of if two distinct clusters are detected within one found class, the class is split into two new classes permitting the hearing aid to set a corresponding different parameter set for each of said two new classes, and if one cluster is covering two found classes, the two classes are merged to one new class permitting the hearing aid to set a corresponding new parameter set for the one new class.