Pro 4:25-27 Let your eyes look directly forward, and your gaze be straight before you. Take heed to the path of your feet, then all your ways will be sure. Do not swerve to the right or to the left; turn your foot away from evil.
Proverbs continues to talk about the path, and how to stay on the right one. The correct path gets lighter and lighter, going towards God. This is the good path. When we go towards God, His wisdom can keep us from falling. When we turn to the side, we are not looking at God. It is no longer 100% good, so part of it must tend towards evil.
I've been thinking about this a lot lately. There's something I think God wants me to do, but if it gets close to happening I am afraid. I fear I am not ready. I get anxious. This is exactly what the Bible says will happen if I do not stay focused on God! If I do not keep heading towards God, then I stray from the path and stumble. We are not to be anxious or fear, and both tend to evil.
Psa 37:8 Refrain from anger, and forsake wrath! Fret not yourself; it tends only to evil.
As soon as I let my emotions run their course instead of staying firmly focused on what God wants, all that happens is I grow more and more anxious. If I return to the right path, the anxiety fades.