There are always going to be people that talk down on others just so they can feel better about themselves. People that do that are really empty inside and in fact hate themselves. If you are working towards some goal, especially a big one, there are going to be naysayers and doubters. But they are there for a good reason. Without them, you wouldn't have anyone to prove wrong.
The best way to deal with such people is to stay positive and stay focused. Look ahead and don't look back. There is always a pot of gold at the end of the rainbow. The negative people in your path are just there to keep you from getting that gold because deep down in their mind, they know you deserve it. Like they say, flies pick at the best fruit and if you didn't have any criticism, especially negative criticism, how would you know if you're on the right track?
Whatever you do, don't let negative people get under your skin. Just know that you have something good coming your way. Nothing good ever comes to negative people so of course they are going to be jealous of you. You are running a race and it's important that you keep your eyes on the finish line. You are a winner and winners win, even when they lose. But negative people lose all the time. Stay away from them. Avoid them and surround yourself with positive people.