Should I stop my session for the day and start over, ground myself and pick-up from where I left off or should I incorporate it into the practice? Well, in order to answer this we need to know what the interruption is. Personally, I would recommend differentiating between a physical disturbance and a sensory disturbance.
For example, if a child jumps on you, a dog starts licking your face or you have no choice but to answer the door when the doorbell rings, then I would classify that as a physical interruption and suggest taking a moment before starting over - time permitting of course. However, if you hear the phone ring but don’t need to answer it, your neighbours turn up the music, or there is any other interruption which is unsettling (but doesn’t actually cause you to move) then you can simply incorporate it into your practice.
So, you may hear the distraction and experience some frustration. Ok, feel the frustration, watch it pass and come back to the breath. If the distraction continues, rather than fighting with it and struggling to come back to the breath, give the disturbance your full attention, whether it’s a sound, smell, sensation or whatever else. By making it your new point of focus, you make use of it and it ceases to become a disturbance. You may well still experience some frustration, but allow that to happen, see it clearly, look into it and understand from where that frustration arises. This way, we are able to bring everything into our meditation practice.