Two things that I did have to justify (and probably aren't the best). The first was kind of a major life event where I stayed in the band that I was in long past when I should have. I justified that I should stay because the people were in my friends and I didn't want to unhinge the entire group by leaving. But it was best to leave because I think deep down none of us were really fully enjoying the experience anymore and just holding on because the others were.

The second thing that I tend to justify is bad food choices if I've had a really rough day, though the food doesn't usually make me feel any better, so I probably shouldn't do that lol

Something that I disagree with other people justifying is group mentality to dismiss decisions. For example, "why should I pick up my trash when nobody else is?", "why should I recycle if my friend doesn't", etc. Basically using a generalization to justify not doing something that people should be doing is what I disagree with.