Did you really never have ongoing romantic tension with someone you interacted with regularly? It seems rather inevitable for young people to find themselves in one of these. Even the loneliest people I know have mustered up some kind of tension with someone, even if they were never able to act on it.
Unfortunately, I got turned down several times. One initially said yes, then quickly changed her mind within the hour, saying she wanted to avoid getting distracted from academics. So, I never had the opportunity to date in high school or my late teens, though I did have the chance in my early twenties.
As an aside: From a research perspective, I'm unsure if the feelings were mutual in many of these cases. As the Scientific American reports [1]: "Men were much more attracted to their female friends than vice versa. Men were also more likely than women to think that their opposite-sex friends were attracted to them—a clearly misguided belief. In fact, men’s estimates of how attractive they were to their female friends had virtually nothing to do with how these women actually felt, and almost everything to do with how the men themselves felt—basically, males assumed that any romantic attraction they experienced was mutual, and were blind to the actual level of romantic interest felt by their female friends."
I suppose that if my current partner were to tragically and unexpectedly wish to break up, I may be able to enter a new relationship after being very sad for a while. However, learning from my teenage years, I would likely avoid dating friends even if I perceive tension (to avoid changing the friendship, as I have in the past), as I don't think there is a reliable way to figure out if someone is interested according to research.
[1] https://www.scientificamerican.com/article/men-and-women-can...
Interestingly, that goes against my experience. At university, there were a number of girls that I liked but considered way out of my class, that I later learned fancied the pants off me.
There were also girls that I knew fancied the pants off me, but I wasn't having any of it, because I thought they were clingy, or too crazy (even for me). I'm pretty sure I dodged a couple of bullets back then.
> Even the loneliest people I know have mustered up some kind of tension with someone, even if they were never able to act on it.
Guess you don't know many people then