Just keep working with them. Haul them out and about. Get them used to different locations and learn that they are expected to behave away from home as well as at home. We pony our yearlings, lightly lunge them, teach them to have patience, stand tied & cross-tied, handle their feet & ears, load (and STAND) in a trailer, ground-drive. Once they ground-drive take them out on the trail ground-driving them if you have a safe enough area. Let others handle them. Basically spend the year setting up the foundation for everything to come. Rinse & repeat - OVER & OVER & OVER again.