Brand, thing, behavior, method, advice, mantra, etc.
I swear by Blackwing pencils.
Also, the 'two minute rule', which has really improved my life: "if it takes two minutes or less to do, just do it now; if it takes longer, schedule it." I've got untreated attention issues and it's very easy for me to notice something needing done, and overlook or procrastinate it because it seems inconvenient in the moment. Having a totally painless rule that forces me to acknowledge that thing I should pick up, that trash bag I should change, etc, or, to at least put on my calendar anything I mustn't forget in the long run has been great for me.
Brew your own coffee. I used to drink instant coffee (think nescafe but with lots of sugar) or just buy from coffesshops. Now I just buy the beans I love, grind some and make it the way I want (how strong or milky etc). I no longer have acid reflux from goddamn instant coffee powder and stay fit since I don't put any sugar in it. Also saves some money from buying in coffeeshop everyday.
I have a buddy that puts hundreds of dollars into the fanciest coffee machines he can buy. He buys bags of beans from all over the world.
I have a $20 grinder, a $11 coffee pot from Kroger purchased in 2013, and while I do buy nice bags of coffee several times a a year, my typical bag is store brand who bean for $7 and I'll splurge on a nice $15 bag from time to time.
I can't tell the difference in taste when I am at his place. However, instant coffee is disgusting and I cannot sip it without a shit load of creamer to dilute the awfulness.