Anybody you like can be the love of your life. This notion that fate has a special person just for you is Hollywood nonsense. Find someone who's worth it, and make them the love of your life.

This doesn't sound like healthy behavior or a realistic view of other people.

How often are you let down or find that your experience with someone else isn't reciprocated?

Can’t say I’ve ever really had that train of thought. Or if I did, it was just a passing thought, not something I’d think about for minutes or hours.

I have indulged in these fantasies many times - it's not unusual to think about hypothetical futures and it's especially not uncommon to come up with stories about those hypothetical futures. It's even more common for you to be the main character of these hypotheticals. It's never been compulsory, I often have to stop my mind from wandering and these thoughts are no different from any others. Fantasies like these are essentially nothing more than a fanfiction of the real world.

What's more important is how you analyze these thoughts and what you feel about having them. If they are actually concerning to you and you are worried about controlling these types of fantasies, go to your doctor and get some referrals for therapy or counseling - many scams exist that specifically target men for especially this type of psych stuff, so try to stick to professional channels whenever possible.

Sounds like endogenous FOMO colored by situational loneliness due to social isolation.

My top recommendation would be to find social activities to participate in. Book clubs, social sports, interest-related meetups, etc.

The reason is that isolation makes it easy to develop for others feelings that are less accountable to reality. These feelings can be positive or negative, and the others can be individuals or large groups of people, but the effect is the same.

Spending time with people is the natural remedy. The more you understand others, the more you understand yourself, and the easier it becomes to appreciate others for who they are without defining your self by them (aka “attachment”).

TL;DR: Get to know people, all kinds of people, and you will discover the natural remedy for these intrusive feelings of attachment.

When I was between the ages of, I dunno, 12 and 22? All the time. Probably not at first sight though, I mean I'd usually have at least some sense of what kind of person they are. Not so much as an adult, though.

Lookup Crappy Childhood Fairy on the tube. Then search for videos on Limerence.

I've only ever had that once, with the mother of my children. It was love at first sight pretty much.