Have you ever tried to look over your shoulder and walk straight? I've done that before and had a few knots on my head to show for it. When you drive a car and turn your head there is a natural tendency for the car to drift in that direction. We are designed to follow our eyes.
Where your eyes go, generally, your feet will follow. So if you walk down a straight path and turn your eyes to the side you are likely to wander off the path. Until you fix your gaze back on the path you will continue to stay off course.
Jesus tells us that the gate is small and the road is narrow that leads to life, and only a few find it. So keep your eyes straight and fixed on him so that you stay on the road and follow him. He will lead you and show you the way!
Proverbs 4:25-26 (NLT) - "Look straight ahead, and fix your eyes on what lies before you. Mark out a straight path for your feet; stay on the safe path."