Sadly, some people take delight in destructive criticism. Constructive, caring criticism is very useful and necessary. But criticism for its own sake is something to simply ignore. Small minded people think that somehow they can improve their own lot by putting down others. Nothing could be further from the truth.
True success comes only from providing something of value to the world.
Your dreams, your ambitions do not diminish the lives of others. When you improve your own life, you cannot help but improve the lives of those around you.