Always smile! Even if you're scared, if you smile, you will relax.
Once you are relaxed, everything else will follow.
Don't let your horse refuse, If he does then take him over it again. Don't let him slow down after the jump, if anything, speed up. Look ahead, Have fun!
P.S. When you get a bit more confident, Practising for jump offs (i.e. Tight corners) is really good practise and great fun.