Why do my friendly thoughts seem to deter people? ?

For example, when i meet someone in a store, a worker or stranger, and we greet/make small talk etc. Then i leave and think what a cool/nice/interesting person they were, and look forward to hopefully seeing them again and saying hello- or whatever, even thinking maybe we could wind up being friends. What always ends up happening is that when i see them again, expecting to say Hi, hows it going, they are either not friendly or they arent there at that time. It almost feels like my thoughts directly deter any connection or vibe that i may have felt the time before. Hence why it has been impossible to find any friends (my age) and also to find love. Maybe a little hard to explain, i know workers have a job to do and being nice is part of that, but thats not what i mean. Is there any psychology behind this?