Start being a passenger....
Find yourself a flying buddy.
Someone who can fly and navigate (and who you get on with) and navigate with them while they're flying. I'm not saying get them to teach you...but someone else holding the pole while you're looking at what's going past the window is a great way to relax and 'see what your map is actually telling you'. If you can't already do this with your instructor.
Go back to basics....with short routes to places that are obvious. Do the planning and fly the leg to the plan, watching for the first sign of the plan not being quite right then adjusting the plan to the live winds.
Spilt one long leg into 3 or 4 short ones with regular timing and check features. Study what you're expecting to see as you leave each checkpoint and do your GE check to make sure you're starting from the right place and heading in the right direction.
If you have a 'featureless' route (long periods of the same forest or desert) then find a feature and plan to fly to that even if it's slightly off your direct route. Hold your heading and speed as accurately as possible, with regular 'FREDA' checks. If you can, get as high as the airspace allows - a much better view of the whole picture and less detail to distract.
Until you're comfortable with the basics again, I would recommend against rushing out and buying a GPS - even though the temptation will be strong to have confirmation from the satelite gods as to where you are. Once you're comfortable with the basics again then think about 'grabbing a Garmin' to reinforce the visual.
HTH