I think because of mistakes I've made in life I will never find my soulmate
Everyone can find a soulmate. What kind of mistakes are you talking about?
One night I had sex with a stranger, but it was so bad that it's not even worth remembering.
I can understand your frustration, but you shouldn't be so hard on yourself, there is no point. If you keep doing that, you will never be happy enough to attract another person, so you will end up alone. You should shake it off and look for love in unexpected places.
Wtf I thought we all deserved to find our soulmate and that's all about luck
It might partially be about luck, but you'll have to get out there and look for one. Once you get yourself out there being social, then you might get lucky to be in the same place as your soulmate.