You are a kind of bad person if the person you called your best friend is winning and you are not happy for his success. However if y>your friend is winning more than you do, the best thing to do is to ask him to teach you have he predict his games or if possible also stake on the same games with the same predictions with him. Success is not a thing one should be angry about, mostly if it happens to someone closer to you.
Success from gamble has time and season, when it always reaching you, you just grab it because no body knows if the next predictions will not work well. As you are angry for your friends winning, it means you won't be happy when you too are winning. Moreover it's only a greedy person that doesn't feel happy when someone closer to them is winning and they are losing. The important thing someone who's losing is supposed to do is pray for his own winnings to come.