I've had this happen twice with ideas I was actively pursuing. Both turned into YC companies, both successful, the latter meteorically so. How you should respo

I've had this happen twice with ideas I was actively pursuing. Both turned into YC companies, both successful, the latter meteorically so. How you should respond often is dependent on the situation. The hard part is that the only person who is truly acquainted with the relevant facts is you (and your co-founder, if you are so fortunate). The first time, I was blindsided by the launch of a startup I should have known existed. Despite doing tons of market research, it somehow flew under my radar, and the result was that I ended up wasting months of my time. In that case, deciding not to play catch up to a company with more traction, funding and resources than I had, in a space with very little room for differentiation, was probably the right call to make. It burned, but in hindsight the decision to move on was almost certainly for the better. Using that experience as a catalyst for the idea that followed, the second time there would be no blindsiding. Instead, I became aware of the other startup almost as soon as it came into existence. While not a threat initially, I watched over the course of a year as it became more and more similar to what I was working on, gaining incredible amounts of traction along the way. It felt like my product was dying in slow motion before even being born. The only difference this time, was the particular space allowed for quite a bit of differentiation. While that's a good thing, it also makes the questions you have to ask yourself that much harder. After agonizing for quite some time, I came to realize most of my fears were irrational. Internalizing what it truly meant to have a second mover advantage helped tremendously on this front. Now I think in terms of celebrating their success, and building off of it every way I can (in an ethical manner). The more successful they are, the more successful my product will be. For anyone in a similar situation: chin up, don't torture yourself, and try to build off of it in a positive way. It might have been that you were only in competition with yourself.