I think you need to examine some of the issues you have encountered as a developer where you pulled your hair out after you had to revise your code for the 10th time because of a yet another design change. You probably have a list of projects where you felt that there was a lot of rework and pain.
From that list you can derive the scenarios that the Design Patterns intend to solve. Has there been a time where you needed to perform the same series of actions on different sets of data? Will you need to be able to future capability to an application but want to avoid reworking all your logic for existing classes? Start with those scenarios and return to the catalog of patterns and their respective problems they are supposed to solve. You are likely to see some matches between the GoF and your library of projects.
