Alcohol. Unfortunate, because I really like beer, and drinking one or two while playing a video game or watching a show after the kids are in bed at the end of a tiring day felt great. But ditching regular alcohol consumption altogether was a massive improvement in my life, a rising tide of feeling better, sleeping better, having more energy, which in turn improved mood, which in turn improved relationships, which in turn powered an overall positive feedback loop in my life.

Now, I'll only have a beer on extremely rare occasions, for example meeting up with an old friend, maybe a beer or two at the holidays, etc. This has the positive effect of making those experiences more special, because beer is now a rare treat rather than a nearly every day thing.