I guess it depends how you look. If you see her so you don't collide with her, that's one thing. If you look at her and allow your thoughts to go into deep chambers of the forbidden, that can be draining for many people. Precisely why is a complex question. One reason is that to sustain one's power of imagination in this area, requires great sacrifice from other tasks that require our attention.
for instance, I once glanced for one second too long while driving. My wife said, why did the car swerve. I lied and said I was looking at a restaurant. She said which restaurant. I made up another lie. Then she said, you weren't looking at a restaurant were you. By this point, I was exhausted from lying. Hey, how did I get so tired!! I was sitting in the car the entire time!!
