“How should I gain confidence?”
I bet loads of goalkeepers ask this question to themselves. And the answer is not very hard, whenever you concede a goal, never take it as a bad thing, most goalkeepers are furious when the get conceded on. The way i take it is either by laughing it off or rebuilding my commitment into the next future minutes in the game. Think about how you conceded and how you should work on it, you can always go to a public football pitch/field and improve on the mistakes that have happened in a game you have just recently played in!