A one-off situation I don't think is stalking. It is most definitely a slippery slope and could lead in to full blown stalking in the future.

OP I think you're human and vulnerable and can understand why you did this. But I think it's good you are recognizing and want to get a handle on it right away.
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Second thought: I think it's interesting people have these different opinions. They talk about stalking behavior as ok if it's not coming from a "dangerous" person. But stalking is stalking whether or not it's coming from a pleasant but vulnerable human being as it is coming from a sociopath. The intent can be different but the behavior can feel threatening in both situations. Intent is NOT all that matters with this. Having someone peeking outside your window can be very alarming whether or not that person has plans to physically harm you. it is potential for psychological harm.