One of the big problems is trigger control. When the gun goes bang, it should be a suprise. Many people will put the the 1st joint of their index finger on the trigger. Incorrect!! The trigger should be behind the cuticle. Don't try and strangle your rifle. Relax. Jerking and flinching are two seperate issues.
Start w/ a larger bore rifle, then shoot a .22lr. Anything you are doing wrong will be magnafied. Switch between them as the day progresses. Breathe, relax.
Get up once and a while and step back.
Freedom is not free. The best of us always leave too soon.