New sights, sounds, smells overwhelm your dog's senses, making it hard to focus on you.
Stress from change, illness, travel or routines being disrupted can impair your dog's training memory.
Over-arousal from seeing other dogs or getting ready to play can make your dog too excited to focus.
Your dog may occasionally blow you off if he's lost interest in the reward being offered.
If you get lazy pronouncing cues, give them in different tones, or give vague hand signals, your dog gets confused.
Lack of Clarity
Skills not regularly practiced and reinforced will erode over time. Daily quick refreshers help.
Teenage dogs mature and push boundaries. Keep training sessions upbeat and structured.