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.
Setting a recurring alarm at 9:30pm and taking melatonin right away. Got me in the habit of getting tired and going to bed more consistently.
IIRC getting up at the same time each morning (including weekends!) is more important than going to bed at a consistent time. Though doing both is best of all.
In particular, if you go to bed late, don't change your waking-up alarm. You'll be a bit tireder the next day, but will probably correct for it automatically by falling asleep faster and sleeping deeper the next night.