"I'm trying to give up chocolate. Last weekend I saw a delicious cake and I found myself telling myself the only reason I wanted it was to boost my energy levels, hahaha you know the feeling, right?" If they didn't immediately chime in with examples I'd prompt them with "and you know, its not just food, I rationalise all the time" and ask them if they do as well.

Over than half of them immediately came up with their own diet-related rationalisations. Of the other 4 I had the "calling my mum" one above, a couple of people who said they often caught themselves coming up with reasons for why they weren't doing their work, and one "the dog wouldn't like to be taken for a walk in this cold weather".

The reason I mentioned guilt is that a few of them (I didn't count) explicitly used the word "guilty" (like, I'm too tired to work, so I don't have to feel guilty that I'm out drinking) and one person talked about trying to make himself feel better.