Personally I don't like to state my plans, I do better work in stealth mode (or do I just enjoy it more ?) ; but my SO hates backing out of her own words and I noticed it's a good incentive for her to push things through.
In this case, the author explains that the rationale is that telling your plans satisfies your self identity enough. I think the degree of "enough" is likely what's driven by personality differences (which are in turn driven by socio- cultural- etc.)
For me, I know that when I tell people stuff (and this also depends on what the "stuff" is, telling people I'm going to eat Chipotle doesn't mean I'll do it) I become very motivated to do it to avoid "losing face."