I think I will be very happy!为何要加be?

I think I will be very happy!为何要加be? i will be happy 为什么加be I will be very happy with You are not happy,you think I will be happy? I think that will be very happy.这句话有没语法错误? you will be very happy to see that i think…这句有没有语病 As long as you smile.I will be very happy. I think we will be very good,I think I have a very important Darling .I am very happy to be your wife .I think it must be I think my winter holiday will be very fun I think we will be I think you will be good friends.为什么要加be