What are your greatest one-shot life improvements?
Problem: I struggle with sleep. Both getting to sleep and staying asleep.
Solution: Custom gel earplugs, and soft fleece eyemask.
Comment: I'm sensitive to light and sound, so the slightest noises and early morning light will wake me up. I didn't realise this may be the cause of the problem until three years ago; people told me it was because I was depressed, but it was the other way around. I tried a bunch of solutions but they were all irritating, and the plugs icky or wasteful. So I went to my local opticians for my earplugs (best £100 life spend.) And for the mask I found a material that didn't itch on my skin with soft pressure, and made it into a headband. I used to be a sleepless mess until my twenties. This was a big change.