Let me share one of my classic goofs! When new to photography and being a callow youth of about 13, I had mixed up some fresh fixer. I didn't label the bottle, relying on the "pickle" scent to distinguish it from the also unmarked developer. You folks can predict the outcome. I had a cold.... I couldn't smell the fixer, and I fixed the film in that fresh stuff. All gone.

Just recently I pre-loaded two daylight tanks. Must be genetic, I didn't label either. I souped one, then decided to do the other later. Again, you can see what's coming. All gone. Just the merest exposure in dim room light. 400ASA film. Now if I preload I put a strip of masking tape over the top, labeled with what the film is. So far, so good .... Until my next error.