Half your body weight
Speaking of the amount of weight we feel comfortable carrying with us, I just thought I'd mention ...
Through my experiences, I have found that when I'm cycle touring, if the weight of everything I bring comes to half my body weight or less, I can tour quite comfortably. But if the total weight is more than half my body weight, that's when I really start to struggle ... especially on the climbs ... and that's when I feel like cycletouring is more work than fun. It's difficult for me to pedal all that around, it's difficult to walk and push the bicycle, and it is difficult to haul it all up into a hostel or wherever.
That total weight includes:
-- the bicycle
-- racks, panniers, and other bags
-- everything I put in the panniers and other bags