You can't, it's logical and understandable for a player to resign when he sees he can't win the game. Personally, I don't understand in what it is a problem for you because :
- You win Elo faster
- You can go to another game and challenge another player.
So I have this problem where my opponents keep resigning. I swear it's always when I take a valuable piece. Is there a way to prevent this or not?