I agree with OneTooMany. For food, you should give him free choice of orchard grass or oat hay so that his tummy has something to digest and he feels satisfied when you want to work with him. You should take it slow with him and do some different things: poles, low jumping, trail riding. He's 3 and his attention span isn't fully there yet and he may be bored with doing the same thing everyday. Don't worry, just have patience and take it slow, little by little he'll come around ;) Good luck!
John 14:6 - Jesus said unto him, "I am the way, the truth, and the life: no man cometh unto the Father, but by Me."