Repositories are awesome, and we should have more of them.
I recently completed BJ Fogg's Tiny Habits, and it's a pretty lightweight way to install new habits (recommended). However, I realized I could use a better repository of useful habits.
So, please use this thread to suggest habits that you've found useful. Bonus points for evidence/anecdata of usefulness.
Obviously, 1 habit per comment makes upvotes a clearer signal of collective approval.
Before I started a family, I went through a period of minimalism, and I had a "magic" wallet (card-sized, flips money across on the inside using elasticised bands, doesn't fit coins), and only carried that, my phone and keys. I couldn't collect receipts, lots of store cards, coins, tags or whatever else in it, and it had what I needed (back then).
(separate comments for separate habits, as per the original post)