A Goalkeeper is a very important person in a football team. He is the 'last line of defence' and his performance can have a big effect on the rest of his team. If he consistently plays well his team have confidence in him and know that he can be the difference between winning and losing a game. If a Goalkeeper is inconsistent it can effect the confidence of the team and make them nervous.
One very consistent Goalkeeper was Ex-Manchester United player Edwin van der Sar. In one season he kept a clean sheet (or stopped the ball from entering the goal) for 1302 minutes (almost 15 matches) which was a world record for a single season. He was a calm influence who never got rattled and the defenders in front of him knew that they could depend on him to do his job. Being consistent in sport is an important quality. It is great to see a player who consistently performs well and works hard.
In the Bible we can learn a lot about God and his character. One of the things that stands out is how much he loves us, so much so that he sacrificed his son for us, and also that this love doesn't change. In the book of Malachi God sends a messenger to his people to say that they have forgotten him, they no longer worship him and that they have done wrong. While God consistently loves us he also consistently hates it when we do wrong. The messenger asks the people to turn back to God because, despite what they have done, he still loves them. In Malachi 3:6 God says "I am the Lord, and I do not change." God is consistent in his love for us and that should give us confidence in him.