The part of the brain that most often interferes with mindfulness is our frontal lobe in the place where executive functions rule. It’s where we make judgements about the world and formulate our important decisions about how to engage in the reality around us.
As dogs have evolved, they’ve acquired a complex of emotions that mirrors ours. Yet, they lack the sophisticated executive functions that get in the way.
When dogs are distressed they can experience fear about what will happen to them. They can dwell on bad experiences in the past. In other words they get taken out of the present.
When your dog is happily romping around and carefree it’s in the moment. Its mind is filled with what’s happening now and everything that’s around it. No worries. Canine mindfulness.
A lot of this is speculation, simply based on observing dog behavior. Regardless, maybe once in awhile you should mirror this state of mind that your happy romping dog appears to have?