Everyone is against you. Never forget that. But there are a few laws of the game that can help goalkeepers. Not every ref knows or applies them properly, however. If you know them yourself, you can always give a gentle reminder. I'm not claiming that knowing these laws will save your life, but if you play long enough, knowing them might come in handy once or twice. So let's start with...
1. When you have possession of the ball and are trying to distribute, opposition players are not allowed to impede you in any way.
Too many times over the years, I've watched a goalkeeper try to distribute while being hounded by an opposition player moving into his path, trying to (or just acting like) he's going to charge down a kick from hands. This is NOT ALLOWED. From the Official FIFA Laws of the Game:
An indirect free kick is also awarded to the opposing team if, in the opinion of the referee, a player prevents the goalkeeper releasing the ball with his hands.
If a player does this to you, alert the referee and hope he understands the law.
2. A player taking a free kick, corner, or penalty cannot be the first player to touch the ball if it comes off the post.
You might not think this happens often, but I've seen it at least three times: twice in games when I was coaching, and once in a Premier League game. Morten Gamst Pederson of Blackburn bent a free kick over the wall from a wide position, watched it smack against the near post, and then was the first player to chase it down. He sent in a cross that was headed narrowly wide. None of the opposition players - nor, indeed, the refs - noticed the breach in the law. If you're in goal and this happens, make damn sure they notice.
3. You cannot be offside directly from a goal kick.
It's amazing how few people know this law. I know a few who don't: Shay Given and the Republic of Ireland back four. In a friendly against Argentina a few years ago, Gonzalo Higuain stood twenty yards behind the last defenders as Argentina keeper Sergio Romero took a goal kick. The ball sailed over everyone right to Higuain, who may or may not have touched it before Angel Di Maria scored. Now - complicating things a little - if he DID touch it, Di Maria should have been flagged offside, as he was in an offside position. But Given and the defenders protested to the ref about Higuain, whom they thought was miles offside, and not DiMaria, who was only marginally off.
The point is, be aware of this whether it's you or the opposition keeper taking the goal kick. Don't let a striker wander in behind your back four. And if you've got the leg for it, have one of your strikers go stand behind the back four and see if they let him.