Falling in love is the easy part. Too many people though mistake being "in love" with long term sustainable love.
When you are getting affection, adoration and sex from somebody new it's REALLY easy to be "in love" or more likely "in lust".
Eventually that high is not so present though and a deeper love has to develop or the R will not grow. I can't remember the exact number but I think it's anywhere from 18-36 months for the "high" feeling to move to normalcy.
It's comical (and hurtful of course) when a spouse proclaims they are "in love" with the OW/OM. As my H is learning almost 3 years later he was VERY in lust and now, well, now real life is back and it's not all he thought it would be.
When one's biggest decision is who's apartment to sleep at or where to go to dinner I'd imagine life *is* pretty easy!
I guess it goes both ways though and that is why the LBS is warned about rebound R's.
Most people are very ill prepared for marriage. Everybody believes that "love" will see you through. Making divorce laws more stringent won't do a thing as people will do what they have to do to get out of a situation. Funny though people don't go to any great lengths to get IN the situation of marriage.