[@Angel Vicky] You can absolutely feel disappointed about that! Your bond to your partner is a very basic instinct, but it doesn't stop you from having opinions or problems. The euphoria only lasts a few seconds when you first reunite, after that the affect of your soul bond is initially just that that longing feeling you've been experiencing your whole life is gone. The bond will grow stronger over time, but once again, it's a very personal thing. I assume in this case, you're thinking of a pair who know their soul bond right away? If so, it's totally reasonable to be upset that your bond is platonic when you've been hoping for a romantic one your whole life. After all, the fantasy you'd been building just got basically wrecked XD 

It's kind of hard to answer questions like that in full because everything is so personal, but I hope that makes sense! Feel free to keep grilling me until I make sense (I recommend joining the discord server too!)

As for prior relationships, this is one of those spots where people realize that being Reunited can sometimes suck. Say you have a girlfriend going into it, but then you find your soulmate and realize you have a romantic bond. Well, the way you realize this is probably because you're feeling a romantic attraction to your soulmate that trumps any other romantic feelings you've ever had before. If you try to fight it and stay with your girlfriend, it's entirely possible that your soulmate will get jealous (after all, they are still a person, and they have just as strong an attraction to you as you do to them) and you'll more than likely find your relationship with your current girlfriend to pale in comparison to the feelings you have for your soulmate. Soul bonds are notorious relationship ruiners; I can go into more detail on that if you'd like as well ^_^