See the light at the end of the tunnel

A tunnel is a dark place you have to pass through to arrive somewhere.
To see the light at the end of the tunnel is to begin to see the end of a difficult situation or period. Here are a few examples:
After working continuously for the past three months, we're finally seeing the light at the end of the tunnel.
You'll feel better when you see the light at the end of the tunnel!
The worst part of a project is when you can't see the light at the end of the tunnel.