I just started using a prescription eye drop, and it costs $40 for a TINY bottle.
I thought I'd used up the whole bottle -- it was sort of spurting and bubbling, and it was hard to get a full drop out -- but for some reason I thought to turn the bottle upside down (trapped inside a roll of tape so it's standing straight up on its nose), and I've had FOUR DAYS of drops out of a bottle I thought was empty, and I think I'll get at least one more day tomorrow! I genuinely asked myself, "Did I open the new bottle? Am I confused?" but, no, the new bottle is still in its cardboard box.
So, the question is, What are you throwing away before it's completely used up? STOP IT!