K.I.S.S.......
Some personal events that have happened to me over the last eighteen years come to mind.......
I'm flying DR Waltham to Henstridge (I have no GPS.....

) with an experienced rotary pilot next to me....unknown to us, westerly headings on the compass are 15-20 degrees out!! A quick call to 121.5 soon puts us back on track......
I recently get radio failure about to call Farnboro radar on a trip from Waltham to Goodwood. Squawk 7600 and after landing back at Waltham they inform me that Farnboro rang them on the landline to let them know a plane with radio failure was returning!! Comforting to know it works.....
Having visited D&D some years ago, we watched as an incident with a Tornado unfold on the Scottish borders -as soon as the pilot announced his problem, various red lines appeared on their map display from slave radar stations around the country, pinpointing the problem a/c -same would happen if you squawk 7700. Another comforting event!
Flying IMC from the north back to Waltham some years ago, I inadvertently select 7700 instead of 7000 after dumping Luton Radar. When I realised I spoke to D&D to let them know it WASN'T an emergency -they said, 'yes, we saw you and thanks for letting us know.'
Just going back to the training, isn't this covered in the sillybus any more -I remember a number of practice calls, both MAYDAY and PAN -OP should talk to an instructor and go and do some -it's no big deal!!!
Oh, and K.I.S.S.?
Keep It Simple Stupid..........
PS I may be Old School -but I'm concerned at the number of posters relying on GPS......