The Light at the End of the Tunnel

Is there always a light at the end? Common sense dictates that there always is. There are, however, reasons why we can't always see it.
Two scenarios that hold some kind of hope are..

1. The tunnel is long and the light is presently beyond our visual range..
2. There is a curve or gradual change of elevation in the tunnel of which we are blissfully unaware..

Not being able to see a light presents us with other possibilities of a more negative nature..

1. Whoever or whatever we seek at the other end has turned the light off..
2. We have mistakenly entered a cave..

Endurance, a key factor when negotiating tunnels, can be tempered by many things, the most important being the joy of reaching what we hope will turn out to be a perceptible gain at the other end.

I find myself in a tunnel presently, endurance and faith (yes, we need this too) are not in short supply, and I know that there is a light at the end.