I've experienced that too. . . here is my reply and advice to you . . .
If when you do not agree with someone they tell you "you're overreacting" or when someone tries to discredit your accomplishments, character or life and when responding with justified statements or frustration, anger or upset are told "you are unstable" . . . remember . . . the person or people that feel the need to do these things are projecting their own insecurities and inner dark struggles. It is they that lack moral fibre, ethics and professionalism . . . Their endless attack on you means you are doing something right and shows them as cowards reflecting themselves as being trapped within what they cannot change, jealous that you can and envious of who you are and what you have achieved beyond what their tiny little narrow minds can comprehend. They may attest to 'know' what you achieved but in reality cannot due to lack of experience or actually achieving themselves. Realise this - you are not 'overreacting' if you 'dare' disagree with someone nor are you 'unstable' if after being attacked you react with some emotion...in reality all it means is you are NORMAL dealing with some very ABNMORMAL BULLSHIT . . . Continue to be yourself and NEVER, never be afraid to be proud of what you have achieved and show it to the world to honour your God (or otherwise if you dont believe in God - your parents who supported you or to honour your family / friends who encouraged you) given talents, skills and attributes. If others cant stand that . . . its their failing NOT yours. Be kind, wish them well and walk away. Let them writh and foam in their negativity and keep shining your light in compassion and love. You know who this is for . . . NEVER NEVER give up and be happy for the haters because it means YOU are doing something RIGHT. Always here for you. xo.... Don't give up because someone or some people project their shame, failings and insecurities on to you . . . they wont change . . . be sad for that . . . and show pity in compassion and forgiveness.