The unexpected. You never know what comes next. You never know what life has reserved for you, what will be the reactions to your actions.
If you have a path, a set of waypoints that you want to follow, thinking "that's the way to get there", you might be confortable with it. But then you start to think: "where is there? Here i am, trying to walk through this, following all this guidelines and signs and stuff. What if i stop and watch what's on the end of the next detour".
Then you start taking some chances. Trying to cut short through here because the road will appear just ahead, but in the end all you get is some scratches and bruises.
Nevertheless you keep going. Now enjoying more the path you're walking. The green of the trees, the cool sound of that bird, some weird insect just calling his mates. And you start to worry less about the destiny and more about the way.
So the next time you get a detour, you appreciate more what new things you'll discover there, new trees, birds and sounds, rather than if that detour will eventually take back to where you were. Because honestly, i don't care where i'll end up next. As long as i enjoy my way there.