They don't believe in you is a mystery. Most of the time, it's because they don't believe in themselves. They can't attain something, so why should you? They fail to see the possible im(possible): the possibility inside of impossibility. Or, some just cannot stand the thought of you succeeding more than them. They put you down, more than anyone you've ever known.
Nice post @javybar & thanks for sharing!
Such a wise opinion. I appreciate it a lot!
Unfortunately, there are also the people that ultimately want to see you fail. (Stay away from those kind of people.) They'll do anything to make sure that you do. Upon your demise, they'll sit back, kick their feet up, eat some popcorn, and enjoy the show.