Teenage dogs have challenges all of their own.Hormones start to kick in from about 6-7 months and last until 2-3 years depending on breed. During this time there are physical changes happening in your dogs brain and body. 

Your once star puppy that would focus, listen and do the behaviours you trained suddenly seems to have forgotten everything. 

*Their recall can start to slide and you don't feel you can always trust them to come back.
*Pulling on the lead slowly increases.
*They show more interest in the environment over you.
*Their response to obedience cues start to disappear.

You may feel like your dog is being deliberately naughty, difficult and disobedient
 
This is not their fault!
They are becoming teenagers
This is a time for patience and guiding  your dog through this time