Love is not just one thing. It's actually four distinct phases: attraction, the dating phase, where you build up the neurotransmitters to fall in love, falling in love, and true love. Men and women fall in love differently. In fact, what causes a woman to fall in love may prevent a man from falling in love. Falling in love is caused by different neurotransmitters increasing to a tipping point. When a man falls in love, his testosterone drops. Researchers at Harvard University found that this drop occurs when a man commits to a woman, so it appears that commitment may be that catalyst for a man to fall in love. Parts of your brain actually deactivate when you fall in love. The ventromedial prefrontal cortex is one of those. It's responsible to judging the other person. That's why they say that love is blind. But, even if you noticed something wrong, it wouldn't register, because the part of the brain that sounds the alarm is deactivated too. The phase of falling in love lasts about two years. After that you get your brain back, including the part responsive for critical judgment. When that happens it can feel like the love is over. But, happy long-term love is possible.