Packing lightly - a sport I'm not trained or qualified for.......

I conducted a trial run of packing for my trip today. I don't think I've mentioned where I plan to go. The intinerary includes Thailand, Vietnam, Cambodia, Kuala Lumpur, Singapore, Australia, New Zealand, Japan and China. Now those who know me well, know that packing lightly is not an art form I have mastered, being the type of gal who likes to be prepared for everything. It's unbelieveable I was never a Girl Guide - went to Guides once, found it boring, regimented and run by women who in a previous life must have worked for a Third Reich kindergarten. The packing progress went like this:
1st attempt - could lift the backpack but could not straighten knees.
2nd attempt - could straighten knees but weight and lack of back strength meant a high possibility of falling backwards onto rucksack and floundering around like a beetle with my legs waving - not a good look in the middle of Baggage Claim.
3rd attempt - by this time I was half emptying any bottle with liquid in. The advice is to walk around the block with the backpack on to see if I can cope with it. I was slightly out of breath walking downstairs and to the door! I'm either going to be seriously fit at the end of this or have a cardiac arrest in the middle of Heathrow before I even get started.