This is great advice, but I think it could be rephrased slightly:
Make sure to always do and finish that which you'll say you'll do. Especially regarding exercise, as without that, your productivity can drop. And if you can't finish, then you'll learn to be more reasonable.
I've been reading HN for over a year even though I'm not the best developer. It simply teaches useful info about how to get things done that I would not get otherwise.
For instance, the case studies on starting a T-shirt company Snowpocalypse 2011 - bam! Knowledge of how to do that. Or the posts on business models in the music industry, links to Mixergy, et cetra, et cetra.
HN basically is extremely entertaining - and the most valuable business site I read.
Make sure to always do and finish that which you'll say you'll do. Especially regarding exercise, as without that, your productivity can drop. And if you can't finish, then you'll learn to be more reasonable.
Anyways, quite solid advice.