Replying to Hitting Bigger Jumps

I have recently joined the park team at my local mountain and the rest of the kids on the team are hitting the bigger jumps the smallest being 18ft me only hitting like 10-15 ft jumps ever I'm really nervous about hitting the 18 ft one. Every time I tell my self I'm gonna hit it I go in and right as I approach it I take a massive speed check losing my speed and then I bail. Any help and suggestions help. +k for helpful answers.