We make promises to ourselves and to others. Some we keep, some we break. The sincere and intellectually honest life is one where you only make a promise when you absolutely know you can keep it based on “historical” evidence. You have to look at what you’ve done in the past, and if you’ve never done it before, don’t promise it.
I think I often make predictions based not on the person I have been up to this point, but based on the person I would like to be. That’s a natural thing to do in some sense, because I’d like to exist in a world where my hard work leads to gradual “improvement”. It’s similar to the natural folly of politicians and economists who base their predictions on the continued economic growth (as measured by U.S. GDP growth) of say 3%.
Running with the analogy of GDP growth… I’m learning more and more that you have to make promises in normal life based on 0% growth or even negative growth. However, set goals of 3% growth to yourself, just don’t announce them. Work your ass off to make it happen, and if you do, people will be happy, and if not, no one will be disappointed because of a broken promise.
I’ve pulled off some very challenging tasks in my life, and because I over-promised, those accomplishments were overshadowed by the small aspects of the promises that were broken.
In my experience, this is especially a big problem in the software engineering world, where programmers make estimates of project completion with the assumption that nothing anywhere will go wrong. Of course, they do, projects are delayed, and the incredibly hard work of the people involved is overshadowed by their failure to reach overly-steep expectations.