More thoughts from my trip to San Francisco. This really happened, and though you may think it's "not so bad," it still shook me.

We waited for the light to change. A fire truck rolled past, and one of the firefighters caught my eye and waved to me. I smiled. It seemed friendly. Yes, potentially flirtatious, but certainly benign.

I left the group as they entered the dance club. Tired feet took me downhill to the hotel. Four men hiked the hill in the other direction. As they approached, one called "Hey." It wasn't a greeting; it was an invitation to a conversation. I pretended not to hear and kept walking.

Another intersection. Another crosswalk. Another light slow to change. A man carrying a shopping bag neared the same stop. He skipped right to "What are you doing out tonight? You're a sweet little thing. You want to get something to eat?"

My training in politeness kicked in, even though he stepped closer, approaching my shoulder, step by step. "No thank you. Have a good night," I said, glad the light had finally turned.

I realized then that those four men walking uphill had triggered something in me. I had weighed them as a possible threat and found them unlikely to be trouble. It was unconsciously done. But the lone man on the corner tripped my alarms and reminded me that those alarms even exist, that out on the street I am always judging men–and occasionally women– for their potential to cause me harm. And that fact scared me.

Someone looking at me would see I was wearing a black pea coat, jeans, and sneakers. Not exactly dressed for attention. It was 1 am. But it doesn't matter what I was wearing, and it doesn't matter what time of day it was. I shouldn't have to spend my energy shielding myself from unwanted attention.