They say it's all about the execution when building a startup...with the caveat that this has to be on the right idea. An idea with a strong product market fit. You find this by launching prototypes and talking to potential customers. Strong emphasis on the latter. 

I've made the mistake in the past of over-executing on an idea that wasn't set on these strong foundations. I deluded myself into willing a market to want a product. I believed something was real because I wanted it to be real. This can be dangerous I think.

Recently, I re-read "Anything You Want" by Derek Sivers and his stories give a clear depiction of how an early stage business should feel. He says it should pull you forward with a positive force. This is instead of it feeling like flogging a dead horse again, and again, and again. 

So in summary, if it feels like you're flogging a dead horse, you're probably doing just that: flogging a dead horse. Beware of your delusions! 

Blind optimism isn't helpful. Cautious optimism probably is?