1. hard headed means "stubborn" or "unwilling to change an opinion or idea
Example: I can't work with Joe any more. He's so hard headed!
2. keep in touch (or "stay in touch") means "do not stop communicating - send letters or call sometimes"
Example: Don't forget to keep in touch. I want to know how you're doing while you're away.
3. miss the boat means "to miss an opportunity"
Example: The sale ends today at noon. If we don't hurry, we're going to miss the boat!
4. be fed up with means "to hate something now, even though I may have liked it before"
Example: I'm fed up with my job! I think I should start looking for a new one.
5.to cram means "to study hard a few days before a test"
Example: If you had studied hard for the past four months, you wouldn't have to cram so much this weekend.