Sometimes, people have life problems that can be entirely solved by doing one thing. (doing X made my life 0.1% better, PERMANENTLY!) These are not things like "This TAP made me exercise more frequently", but rather like "moving my scale into my doorway made me weigh myself more, causing me to exercise more frequently" - a one-shot solution that makes a reasonable amount of progress in solving a problem.
I've found that I've had a couple of life problems that I couldn't solve because I didn't know what the solution was, not because it was hard to solve - once I thought of the solution, implementation was not that difficult. I'm looking to collect various one-shot solutions to problems to expand my solution space, as well as potentially find solutions to problems that I didn't realize I had.
Please only put one problem-solution pair per answer.
Problem: I had a lot of back pain. Some days I'd wake up in pain, and it wouldn't go away for 1-4 days afterwards. Almost once per week? No rhyme or reason.
Solution: Replace the blanket I was using to sleep. My blanket was too small, I would curl up too tightly to stay under it. Now I still very occasionally get the same problem, I'm guessing because of habits, but it's more like once every three months.
Data point: After reading this comment I tried this for like two months - initially intentionally, but also the pillows I had at the time were not right for me and so I kept doing it because getting the right pillow can take a fair amount of time and money. It actually significantly increased back and neck pain for me, I think because my tendency to sleep on my side is just very very strong.