The Light at the End of the Tunnel is a Train

In the first verse, he's talking about a time of perceived stability. Everything is "plain", even, flat, dull. He thought he could "see the light", meaning something on the horizon. Maybe it's something he's been searching for. Or maybe it's something he's terrified of. Whatever it is, it brings with it change.

He confirms that he did see that light, that "distant glow". Is he afraid of it? Is he at peace with it? Either way, he sounds resigned to the fact that the symbolic oncoming train is inevitable.

What "keeps on moving on" could be these events that inevitably pop up on the horizon, barreling at and threatening his status quo. Or it maybe it's him who keeps on moving on, engaged in the perpetual cycle of change, continuing to buy the ticket and take the ride. Either way, "too long" hints at him lamenting these events and his part in them.

He waits for this steadily approaching event, semi-frozen. Should he stop it? Should he adapt? Should he fight it? Anything he's tried has failed, so he gives up and accepts his fate. He can't stop this train.

He repeats the second verse to show how the first train has come and gone, and now another arrives. The cycle repeats. Whatever his failures last time, he's given the next opportunity to make up for them. He doesn't comment on whether or not this is a good thing, or what he can do differently this time, but only that it is.

Once again, he laments the inevitable cycle of change, of struggle, of opportunity, of uncertainty. Here is a man lost in the flux of the universe, whether he likes it or not.