Almost every goalie will one day play in a big game or have already played in a big game. Whether it be the Stanley Cup finals or just a big game decider if you will make playoffs or not. It's so important that you play at your peak performance in these big games. By playing great in big games you will get noticed and get scouted. Most likely you will stand out from the rest as being great under pressure which is a really good quality and what a lot of scouts look for.
The first thing you need to remember when entering any game is that it is just that, a game. You play because you love it. That's why players in the NHL are so good, because they love what they do and if you love it you tend to do better. But even players in the NHL have bad games and sometimes bad games just happen. When going into a big game you need to trust in your skills and believe that you will do well. Believing is huge. If you can believe that you can do it, you can do it. A big key is to start the game by having confidence. To do this you need to just keep telling yourself that you're the best and that nobody can score on you. If you tell yourself that you're going to do well, you will.
All goalies have experienced a game where you feel awesome and you feel on top of everything and everything is just working out. All the saves are just about making themselves and all the fans are going crazy. You need to try and get that same feeling and mindset into your body before your big game. Go for a walk or during your warm-up try and get that mindset for great confidence.
To stay relaxed in a game make sure that you have a good warm-up to build your confidence going into the game. Once you're in the game, what I always do is whenever the whistle goes, I go for a little skate into the corner, stretch or do a little movement drill. Don't do anything that will tire you out for the next play.
Make sure you drink lots of water before and during the game to keep cool and relaxed. Have a little something to eat a few hours before your game so that your totally ready to kick butt and have the best game of you're life.