Soulmate is a person whom you longed for meeting n who matches with you mentally and physically ( 100 %) or matching mutual expectations. So the concept of soulmate is right. But the probability of marrying a soulmate is very narrow. As people say life is a compromise, marriage also becomes a compromise for many.
Life doesn't stop after marrying a soulmate, it actually starts there. Living as soulmate for life time, is more of understanding and flexibility when the priorities change after few years of marriage. Whether you married a soul mate or not, depends on what conclusion you come to after living entire life till death. A person, who may not be a soulmate at the time of marriage , may be a soul mate for lifetime with flexibility and the partner can tell that at the time of death.