Thinking out loud!!

I've pretty much been stumbling through life for the most part.. One thing I've never seemed to get right is relationships. They are complete and utter craziness. From my experience anyway. Why do people portray themselves one way in the beginning then turn out to be completely different in the end? It start by getting to know each other while the excitement builds and the anticipation of what will happen next is in full effect. As you go through the winding river of emotions of the new spark you miss all the important possible red flags that will potentially become problems in the future. Why do we go blind? Why does the heart take over and just paint a beautiful picture of the person just for things to crumble and fall in the long run? Why? Its frustrating to meet someone in hopes they will be honest with you about who they are just to find out that the whole time they were hiding their true identity.