Count your breaths during a stretch of land like a 100 meters or so and compare it to the same distance in dusk and at night. Realizing you are afraid or with some sight problems can eliminate a lot of the problem. You can calm your breath only once you realize you are breathing too fast. You can do everything as long as you remain honest with yourself.
Take your normal street or place you live in and walk a known stretch of it during the day. Stop every 100 meters or as many double steps it takes you to pass 100 meters and look back at the road your took and look for places where you are seen but do not see the observer yourself. Wait till dusk and cover the same stretch of land in the same direction and note how the play of light and shadow creates different blind spots and artificial illumination disrupts the perception of distance and height. Now repeat the drill at full darkness and if your breath changes in speed and depth. Listen to your heart beats and take more time to stop and look back not just into the shadows but to the illumination and what comes off it. Remember to take note of not only what you see but what is missing. Do you have different sounds than during the day, do the people dress differently and what is the minimal range from which you can identify a person or a vehicle ?