If you are always seeing the light at the end of the tunnel, be warned -- it could be an oncoming train.

So says a study published Sunday in Nature Neuroscience which concludes that our well-known penchant for donning rose-tinted glasses may be a failure to store risk awareness in a key part of the brain.

Tali Sharot, a professor at University College London, was intrigued as to why so many people -- even when facing long odds or bleak prospects -- remain stubbornly, even pathologically, optimisitic.