What Am I Riddles

Question: The more it dries, the wetter it becomes.

What is it?

Question: When you fall in me your as happy as could be, but you fall into depression when you lose me.

What am I?

Question: My name can have any letter of the alphabet, but I always have 2 X's.

What am I?

Question: I am alive yet not alive. I can fly yet always on the ground. I am delicate yet can lift tonnes. What am I?

Question: Not chest or box is now discussed. Money can be held in it, but just as we test its metal, within it there is rust.

[What is it?]