Look where you want your wheels to go!
Think about this:
Have you ever spotted a pothole directly ahead -- and ridden right into it? Staring at an obstacle makes your body track to it. Left to its own devices, your body follows your eyes. There are many examples of this phenomenon. Motorists watch you while they're passing and nearly nick your handlebar. Mountain bikers smack into the only rock in the trail. Fighter pilots train on a ground target so intently that they fly right into it.
The way to avoid target fixation is to first look at the obstacle to note its location, then train your eyes on the best line around it. Let your peripheral vision, not your primary vision, keep tabs on whatever it is you want to miss. Practice by using non-threatening obstacles on the road -- leaves, paint splotches, small patches, and so on. You're doing great when you can put your wheels through the gap between the letters in BIKE LANE.
You'll succeed if you remember to NFB:
Notice the obstacle and store its location in your brain.
Focus on the best way past it.
Visualize your wheels going on that good line.
Your bike will miraculously follow the safe path past
the danger.
Just don't dare to sneak a peek as you get
close!