you drift left
you are flying with your left hand on the stick
you get tired and your left hand drops
and the plane goes left
practice, practice, practice
go out to the field as close as you can ( on foot) and watch other landings
you would be surprised at how many pilots inadvertently put in a control movement without intention.
also, do you wear glasses?
you and your instructor need more work...and ask for a lesson with a different instructor. try making a box with the nose of the plane, keeping wings level, using rudder and get a better feel for things ( in flight at safe altitude)
also, refresh your knowledge of rudder useage and "P" factor for both takeoff ,climb, descent and landing