Being in love with someone is truly the best feeling you will ever experience, that is if they love you back. But having that taken away is the worst feeling you will ever feel. Heartbreak feels like being stabbed and feeling hopeless, feeling there's nothing to live for anymore.
I've actually never been in love but I'd imagine it would be just being completely and 100% comfortable around each other. No awkward silences. No feeling insecure if they touched you anywhere you felt self-conscious about. You would never even want to be spending every second of your free time together because you just would be. And despite having comfortable silences, the conversations you would have would be amazing, and would be about anything and everything.
And most importantly you would just be totally 100% yourself around each other. I've had two ex-boyfriends and each relationship only lasted 4-5 months, and in hindsight I wouldn't even call them relationships. I would just say "we were seeing each other" because I never felt like I was truly being myself around them. I was being this edited version of myself and would say the things I thought I should say or do the things I thought I should do. Your first relationships are all going to be awkward af in hindsight. Very rarely will it be true love. You just feel this pressure that it's time to go find love, and you should never go looking for love. If you do, it's fake from the very beginning and you're fighting to turn it into something. It should be natural and incidental, or friends first, or the chemistry when you first meet should be crazy.