Why do I cry during movies?

I was watching movie Knowing and ending parts about 4 angels bring kids to new world before end of the world make me sad...other movie Fast & Furious ending parts make me feel sad too. Because I remembered from The Fast and the Furious all Dom's friends and his girlfriend, Letty. Now Fast & Furious some of Dom's friends and his girlfriend died. Dom and Brain O'Connor became friend, Dom got sentence 25 yrs to life and Brain came to recuse* him. Why do I keep cry when I watch any movie ending parts?