Packing light - hump day

I've been wearing a very small pack the last few days, but today I'll ditch just about everything. What sense does it make to carry all kinds of extra gear "just in case" when all your effort is needed to surmount an obstacle? Take a few things to keep you going (spare tube, patch kit) but forget about covering risks that don't seem likely (no rain forecast - no raincoat). Why burden yourself worrying about things that "might" happen when it's going to take all your energy just to get through an ordeal?