When you are training, don't go straight to the bucket and start throwing marks every time. Mix it up: walk past the bucket, walk in circles around the bucket, go to the bucket sit down blow your call sit there for a min and go back to the holding blind, work from a holding blind (if you're not), walk to the bucket slow and KEEP him at heel, throw a mark and then go back to the holding blind and don't let him have it. These are all just suggestions use them or don't some may help some may not. The dog is excited to get to the bucket and he knows the bucket means marks, plus tests are a very exciting atmosphere which adds to the antisipation for him (and you). As someone else mentioned, try to find a club or a group of guys to train with. If you can work with other people and dogs it will help with the excitment a bit. Good luck.
And you need to train coming out of a holding blind to line which is often not done when training - of truck to line. Should be off truck to holding blind.
This might help.
The Hunt Test Wise Dog (link)