Facing Unfair Job Threats from My Boss: How Can I Protect My Employment?

Hi, I have been working in an MNC company for the last four years in the Marketing department at a middle management level. Due to some personal reasons, my boss is threatening to terminate my employment as he has a very good relationship with one of the top officials of the company. Please let me know the ways in which I can defend myself and prove him wrong.

"Don't pick a job. Pick a boss. Your first boss is the biggest factor in your career success. A boss who doesn't trust you won't give you opportunities to grow." ~William Raduchel. Better wait/start searching for a good opportunity and jump out. "When it is obvious that goals can't be reached, don't adjust the goals, but adjust the action steps." - Confucius