Its hard to give up riddle

Question: It's hard to give up.Remove part of it and you still have a bit.Remove another part, but bit is still there.Remove another and it remains.What is it?

Question: What do you call a sad bird?

Question: What has a bed that you can't sleep in?

Question: How are doughnuts and golf alike?

Question: What can be broken but never forgotten?

Question: People see through me, but none pass through without killing me. I can be anywhere, and can be seen double or single. What am I?