There are many people out there that simply will not want others to be happy. Some may reject any good idea you have come up with, or make you feel as if you can not achieve anything because you are not good enough. The only thing to do with people like this is to cut them out of your life. It does not matter what kind of person you are, some people only want to see the negative, and never want other people to succeed further than them. Keeping someone like this in your life will only hurt you, not them. They get a rush from tearing down other people's dreams, as long as their self-confidence is still secure, they will not care who they hurt.
It might be difficult to cut someone like this out of your life, especially if they were a big part of it. I was in this same situation, and I needed to make the decision to distance myself. Apart from doing this, they made it much easier to completely cut them out just by the way they behaved. Even just some distance away, can help you evaluate your own dreams and goals. Having a break from the person who is always saying, "you could never do that," is eye-opening and makes you realize, yes you can. Anyone has the ability to achieve whatever they put their minds too. My life has changed in so many ways after ridding myself from all the negativity. Any real relationship should never feel like a competition. Once this made sense to me, I removed myself, I removed myself from a life of self-doubt and finally let myself understand that I am worthy of so much more. You do not need to feel unworthy ever, if something good happens in your life, be grateful, and do what you can to pay the world back, do not ever think you do not deserve something. There is a reason for everything, and if something good happens, then that just reflects on the person you are. I do believe in karma, and I feel if you give something positive to the world, you will get something in return, whether it be a new opportunity or just a sense of being important. Good things come to good people. The sad thing is, that many of these good people are being undermined by someone. It is not fair. They hide behind their own feelings, afraid to be themselves because they do not want to be rejected. Do not hide. Be whoever you want to be, think whatever you want to think. If someone does not agree who cares? There will be someone who does. Having someone tell you that you are not good enough makes you start to believe it. I could not take that feeling, there was never a time where I did not feel like a disappointment, and for no reason. It did not matter what I did, or how hard I tried, I was never good enough. Even after cutting them out of my life, I thought that I was not good enough to be in their life, and that is not true. They were not good enough to be a part of my life, and certainly not yours.
I sincerely, apologize to anyone who has gone through this. Just remember, that you are good enough. if you believe that you can achieve any goal. Do not put your dreams aside, with the fear of being rejected or told you could never do that. You can. No one should have the power to make someone feel worthless. On some level, whoever is making you feel this way, is jealous or intimidated because deep down they know you can accomplish anything. Instead of encouraging you to be successful, they discourage you, because they fear what you are actually capable of. Keep that in mind next time you hear something negative, translate "you are not capable of doing anything important," into "you would be amazing at anything you do."