In my start-up experiences it seems like some days your on top of the world and others you're certain you're doomed for failure. On some days, you actually feel both. Call it start-up schizophrenia.
I figured out that this chronic condition exists precisely because it happens to be true: every start-up is on the verge of huge success or a huge collapse. That's the nature of the beast. Here's an example: your competitor just got funded. As a result of this, are you now doomed for failure or poised better than ever for greatness? Two good articles examine both sides of this question. The first tells you why this is good news for your company. The second, why it is bad news.
The thing is that they're both 100% correct. Just like its not paranoia if people actually are out to get you, it's not schizophrenia if really do live in a crazy world.