Hiya, Juniper. I've been thinking about your question. I don't know if it can be generalized.
I can only say that for me, I "just knew" when I've loved someone. The fluttering heart, lots of laughs, and all that stuff was the early part...a sort of infatuation, almost. After that, it was knowing that I cared about the person and wanted to be with him through good and bad.
I think it's different for each person because we're all different, and every relationship is different. Also, I think "love" changes and grows over time, so it's not the same at every stage of the relationship.
It is hard to describe. You just know when you're in love. For me when I realised that I was truely in love, I had made a disastrous meal for my fiance and we just laughed and took the piss out of my disaster and hard potatoes lol. I looked at him and I just knew.
I, too, believe it's different for everyone. Personally, I thought I had been in love before but now know I've only been in love once.
Almost from the start I couldn't get her out of my head for a minute. I would read her texts and e-mails repeatedly. I would miss her like crazy when we were apart. Just the mere thought of her would bring a smile to my face, a face that until her had rarely smiled.
We broke up over three years ago and I still ache every day for her.
When the thought of them brings a smile to your face unknowingly.
When being apart for the shortest amount of time kills you.
When your thoughts are taken up by them.
When you'd rather not do anything else other than being with them or talking to them.
When your innards tingle when they say something.
And when you can't imagine anyone else better to be part of your life.
The only thing I'm certain of is that you absolutely know when you're in love. Maybe it will hit you all of a sudden but you feel about that person what you don't feel for anyone else, even your family and best friends. It's more than a crush, it's a euphoria. And it doesn't necessarily come at first sight, but I think you always know when you're in love.
Like what everyone has said...you just know...it's like a gut feeling, every thing about that person feels right. it's instant happiness. you feel so many things all at once: happiness, excitement, and a calmness. when you're with that person you feel like the only 2 people around, even in a crowded place, because nobody else matters as much. they're your last thought before bed and your first thought in the morning...
that's how i knew anyway.
I agree that you just know. Butterflies is a sure fire sign. And.. just the fact that you don't want to be apart from that person, they're all you think about, you dream about them, you would do ANYTHING to make sure they don't hurt. You want to be there through thick and thin for them, and you're willing to keep trying, to make the relationship work. They consume your every thought, and you count down the hours till you can next see them, talk to them, touch them. Laughing together, and feeling complete whenever you're together.