So I gave him a challenge, playing on chesskid.com against other kids. I told him: "You don't know them, so don't worry, losing was not that bad. I don't care about results, winning or losing. In fact, I want you to lose. I want you lose 100 games first. I will give you a prize when you reach the goal".
Initially he still played very few games. Every week I reminded him the 100-loss goal. Slowly he got into the habit, losing more games every week. After couple of weeks, after losing 40-some games, he began to have some wins. He could no longer continue his loss stream. Winning games shown up more and more, and he became more confident to play. In half a year, he started to play in tournaments.