Too many people don't give a lot of thought into deciding. 'Is she cute and is the sex good?' are the starting and stopping point.
Most great relationships allow you to be yourself and require some sacrifice. No part of living together with one person for 30 years is natural; you have to work at it. Constantly reevaluate the relationship and actively improve things. And you have to fight some beasts: boredom, apathy, rage, anger, fear, confidence, self image. That's not even the half. A great relationship will make you face all your old demons, like, family, your childhood, etc.
Then you have to buy in to the idea that it's worth it. Hopefully, the pussy was the bomb and you buy in early. Either that or you have a wise old man steering you in the right direction. Or enough societal pressure.
But when you get there, you get a better understanding of how love is a verb. A decision. That you were free to choose anything but you choose love. Hardest shit I've ever done. Period. Just spent a week missing my wife, silently jealous and questioning her every move from afar (she was on a business trip), got some trim and I'm a new person today. The emotions you run thru with a good marriage either prove your worth or destroy you.
That's not even to talk about our artificial barriers we erect: can't date this race or that type, too tall/short, okay job, too frigid/whorey, blah blah blah.