Why do people protect things?

Why do we as human beings feel the desire to protect things? Or, better yet, what makes something worth protecting? We guard and protect things that are near and dear to us, such as a favorite shirt, pair of shoes, or really any item. But what about intangible things like our hearts? Are we that afraid of falling in love, or someone falling in love with us? Why do we hold on to the one thing that if we just let go of, would bring us the greatest happiness and joy. We guard, protect, and hold onto our hearts because we don't like change, espically when we don't know what the changes are gonna be.What dont we just release our clutched grasp and take a chance? Why can't we just realize that with hope, there is chance and change? Why must we protect? Why must we cause fatigue and heartache when we can just let go? So please, I beg you, let go.