A lot of getting good at dirt jumping is just getting comfortable with the jump, with your bike, or just jumping in general. You're going to eat it a bunch of times, that's a given. Anyone who dirt jumps and says they never crashed a lot is full of it. Just keep working at it, it'll come to you and you'll feel a lot more confident about jumping in general. Like fuzz said, lean back a little more and don't put pressure on your bars because it will obviously push your front end down.