$700 Over Grates

If you look at the way some people carry their smartphones, it's no wonder that the cracked screen industry does a thriving business.  To help myself be more cautious, I picture my Pixel 2 as seven, $100 bills (its actual cost to replace) and that I'm walking over grates with large openings ready to swallow my money into a sewer below.  Those imaginary grates are sized to roughly represent the probability that I will lose some, and possibly all, seven Benjamin Franklin's if I don't handle them with the care they deserve.

People act more responsibly when using cash and using this technique leverages that fact.  Try it and see if you notice a difference in your behaviour.