Simply restating what is already obvious from the code adds no value and leads to a false sense of progress and security.

a common pitfall in testing is to hardwire tests to the specifics of an implementation, where those specifics are incidental and have no bearing on the desired functionality.

Reinventing the wheel is as important to a developer's education and skill as weightlifting is to a body builder.

Reinventing the wheel and getting it wrong is more valuable than nailing it first time.

The consequence is that all these kinds of software are viewed as mysterious black boxes that just work.

Once you really understand the problem, go do something involving the creative side of your brain--sketch out the problem, listen to some music, or just take a walk outside.

The trick is that while you're coding, the logical part of your brain is active and the creative side is shut out.

Above all, remember that interfaces exist for the convenience of their users, not their implementers.

...software development as a whole involve a continuous learning process. [...] To avoid wasted work, you must allow time to observe the effects of what you are doing, reflect on the things that you see, and change your behavior accordingly.

If you are trying to be focused and "productive" for more than 30 hours a week, you are probably working too hard. You should consider reducing your workload to become more effective and get more done.