Don't give up. It is the power of competition. First of all if someone is building the same it gives you some validation that your idea might be worth it. Second of all, there will always be a lot of people that look like they are working on the same thing, but the might not.

Do your analysis of the market, and iterate based on customer feedback. Your idea might seem similar, but it might be completely different. The race is not to build your idea, the race is to find out if the idea is worth it or not.