So the concept of 'soulmate' is not the new thing, this concept was there before us for a long time. Since the oldest times people not only talked but also accepted its very idea. Many people who don't believe in this concept, also keep looking for someone who is the best for them.
In many old scriptures this concept was supported by authors. In ancient civilizations like Greek, people believe that every person is born for her/his perfect match. But we are so obsessed with the outside appearance, that we overlook that 'it' feeling. It naturally obvious that we are attracted to that 'soulmate' in not the sexualized but sensualized way. We don't feel good without them, but feel perfectly well when they are around us.
As in Paulo Coelho's book 'BRIDA' - Brida asks Magus,"How would I know who my soulmate is ?" To which Magus replies, "You will see special aura above his shoulder."
It is a fictional description of that 'soulmate' concept; but even in the real world we feel something, which is undescribable for many of us, about him/her. Our eyes lit up whenever we see or talk to them, or even think about them.
That feeling, despite of being undescribable, is very pleasant to us. A sudden mentioning of our soulmate afloat our joy. Even in the most painful times we forget our sufferings if we think about them. They are the ones, who really are made for us. But finding our soulmate is not an easy task. Sometime people spend their whole life to find them. So more romantic is the concept of soulmate, more painful it is to find them.
So if you found yours then you are lucky and if you don't then keep looking for those hidden signs....