Sex until marriage

Does anyone else thinks that having sex until you're married its a little bit scary? I mean what if you wait until then to have it and then discover that it sucks with that person?, I have met couples that went through this and in the end they broke up because I this. You might think that if they separated its because they weren't  meant to be, but I think that sex is a huge part of a relationship, and by personal experiences  I know that even if I love that person sometimes that "sexual chemistry" doesn't exist. What do yo think? No hate, everyone has their own opinion, this is mine