I've always found that fear stems many times from the unknown. The more you know and learn about something, the less scary it turns out to be, because you understand it better. Therefore, maybe research about fulls, drills for them, etc, so that mentally you understand what your body should be doing and just have to match that with what you're physically doing. Also understand that if your coach thinks you are ready to move on to fulls, it must be for a reason! He/She must be confident that you can do it, so be confident in yourself! :) Just take a deep breath and give %110 percent into whatever drill/pass you do......if you do a skill/pass halfway or not at all, then the skill is guaranteed to not get over/be learned!