Answering the Question
Something that took me a while to get the hang of in school was specifically answering the question that was asked. Nothing more, and nothing less.
While undertaking a degree in Science, I found that this was even more important. You can spend all day regurgitating the required framework knowledge to get to the point of explaining how deep-sea bacterial mats can survive, how beta-lactam antibiotics inhibit peptidoglycan cross-linking, or how a graph traversal algorithm works.
You don't need to. You just need to answer the question.
In programming, this principle is easily forgotten as well.
It's fun, upon starting a task, to start designing grand systems; systems with many interlocking pieces, that solve any possible permutation your problem, and do it quickly and elegantly! You can just imagine that with a flick of your finger all the data will be flowing, nay, dancing through your new system before sublimely coming together at the end arranged exactly as you needed. Wonderful.
It's often a much better use of your time to solve exactly the problem you have, and get on with the next task. In effect, just answer the question.
Nothing more, and nothing less.
(Full disclosure: this article is motivated by messing this up for many years past, and many years to come.)