he's working through it
Have you ever seen a dog start to pant when he experiences change or doesn’t get something he wants? If there is something our dogs are struggling with, the way to help them overcome that struggle is by having them practice that stuff until it becomes easy. Independence and calmness are skills that have to be practiced daily to be strengthened and maintained (just like building endurance) so do a lot of this confidence and independence building type work until it becomes easy peasy for him!