it's a long road that has no turning

Wiktionary

1. Suggests that the changes you experience in life, i.e. the turns in the road, make it worth living and a lack or absense of change would be far more mundane.
2. Encouragement when things are not going well. Just as a long road eventually has a turning, problems also eventually have a solution, even though one might have to wait.
3. Contrariwise, it also implies that when things are going well, one can expect to see a reversal of fortunes for the worse. The notion of a road that one travels on, equivalent to the path we are given, or which we follow, is central to the reference.