Courage in goalkeeping is so important. Many aspects of the position require that you stick your head into places that most people wouldn't dare. Sometimes you get kicked in places any sane person definately wouldn't want to get kicked in, but that's just part of the job.
You have to play every game with confidence, and that confidence has to be real, and it has to be evident to those playing with you and against you. You must have an aura about you that says, "Things are under control in MY penalty box." All your catches must be solid, you must never be indecisive, and you must always rule the air! All good goalkeepers have this presence in the nets.
But no doubt, to be a good keeper, you must be willing to work at it and work hard. Goalkeeper training is physically demanding and very fatiguing. You are constantly hitting the ground, getting back up, and diving again. You must be one of the fittest players on the team. Your training is a bit different from that of the other players, as it is more anaerobic than aerobic, but goalkeepers should take pride in working harder than everyone else. You must still try to be a good long distance runner like your field player teammates.
If you get scored on-and every goalkeeper does- you must have the mentality to bounce back right away. Some goalkeepers lose their composure after they let a goal in, but the great ones shake it off because that next save might be the one that wins the game for your team. If you dwell on your mistakes, another ball will be whizzing past your ear before you know it.
Finally, as a goalkeeper, you must take pride in your responsibility to the team as the last defender. Your team must know that they can depend on you. when the shots do come, your teammates need to know that you will be there to bail them out.
That kind of respect is not given. You have to earn it. The harder you fight for the team, the more defensively they will battle for you.