Positive reinforcement is the presentation of reward immediately following a desired behaviour, which will increase and maintain the behaviour in future. Positive reinforcement promotes good dog welfare, an improved dog-owner relationship, and supports the reduction of anxiety. Dogs learn, perform and repeat behaviours willingly and intentionally.
Learning new skills (or revisiting old skills in a new way) will benefit your dog by providing a quality, interesting, rewarding time with you, his owner, which can be built in to a predictable daily routine (routine is needed to support understanding of daily events, reducing the anxiety of uncertainty, whilst giving your dog a sense if control). Your dog will be motivated by the sessions, and whilst focusing on learning (how to get their reward), he will be less focussed on the objects of his anxieties, channelling his energies in a constructive, appropriate way.
It is important when training your dog to avoid providing non-contingent treats (freebies). Instead, use high-quality reinforcers to support positive training outcomes, helping the dog understand that their behavior can influence positive outcomes, which also reduces boredom and anxiety.
Punishment-based (dominance) training techniques (verbal punishers such as angry shouting, staring at the dog in a threatening way, hitting, rolling, scruffing, the use of pain or shock causing devices etc) are harsh methods that do not address underlying emotional problems and can exacerbate anxiety-based behaviours.
Stop any punishment techniques immediately and replace with positive training methods in order to reduce anxiety, increase mental stimulation, improve environmental predictability, and to strengthen the dog-owner bond. Punishment is not conducive to reducing aggression nor fear-based behaviours and may actually increase reactivity or introduce new unwanted behaviours. Stopping punishment and replacing it with non-aversive positive training techniques (teaching the dog what you want them to do instead) will reduce physiological fear responses, improve learning, trust, and welfare.