Why do relationships have to make everyone crazy?

Every relationship I have ever been in except 2 i have gotten really screwed over... Sometimes it's the guy sometimes girls, but why do people feel the need to be with more than one person when you find someone who is so perfect for you?

Sometimes it amazes me that 'we' get so hurt. 'We' are one of the only species who try to meet partners for life. Yet we are by far the most intelligent and therefore the most deceitful. I know I'm no angel when it comes to relationships but I always admit that. All I can say is that if you do meet the right person, who is right for you in every sense of the word he would forgive you anything, never hurt you intentionally and always, always take care of your heart. Good luck and remember the WRONG relationship sucks!