Don’t be sad if your idea is already invented! The process from idea to completed invention is one of massive undertaking. There were many difficulties that arouse on the path. The goal of most ideas is to solve a problem, and if that problem is already solved, its great! You can focus on reaching the greater goal.
Now, there is some compromise. Because this invention was not invented here, some elements of the solution may not be as desired. You need to make a decision here - are these compromises acceptable? If not, your work is not done! You have a reference, but your problem is not truly solved.
One should not simply give up on an idea because something similar has been attempted. One should also not simply pursue an alternate solution without a clear direction.