According to studies, the average person will fall in love an average of seven times before they decide to tie the knot. Falling out of love that many times may make it difficult because it often leads to 'frustration attraction' which is when the person that is broken up with feels even more attracted to the person that dumped him.
What's worse, even after that average of 7 times, that marriage might not even last! The divorce rate for the United States is at around 50% and it's rising every year. Check out this article for advice in how to avoid the ways in which people bring down their relationships