It's disappointing when you realise the great idea you had already exits on the Internet. It may be a success or a parked website, but it means though that others were there before you.
However it's not an excuse not to follow your idea. Execution matters so much that there's little doubt that your project will be very different from the exiting ones you found.
Just make sure you do it slightly differently from the others, that it has a competitive advantage only you can bring.
Remember also that you may be luckier than the others before you. Timing is key, launching at a different time may bring a different outcome, and a great personal experience for sure.