Not surprised you feel a bit down, most people would in that situation.
1. Try and focus on positive thoughts
2. Imagine u are 10 years in the future looking back at this. It really doesn’t matter what this other guy thinks about you. Ignore him and if that doesn’t work, tell him to **** off. Really just say to him, “I don’t care what you think, just **** off and stop harassing me or I’ll just add this to the existing grievance against you”.
3. Keep a diary of everything he does but don’t get upset.
4. Best idea is to remove this guy from your life. Maybe get another job. When it comes down to it, it is the people that make or break jobs. If you do leave, make sure you make the reason clear.
5. If he’s done it to other people that you know, tell them you have brought a case against him, they may do similar or offer support.