Philip Walton, an engineer at Google, wrote a wonderful article that every developer should read. He talks about front-end engineers, but most tips are applicable to back-end engineers as well. A few quotes:

Taking the time to figure out why your hack works may seem costly now, but I promise it’ll save you time in the future. Having a fuller understanding of the systems you’re working within will mean less guess-and-check work going forward.
Solving problems on your own is a great way to learn, but if that’s all you ever do, you’ll plateau pretty quickly. Reading other people’s code opens your mind to new ways of doing things.
In my experience, writing, giving talks, and creating demos has been one of the best ways to force myself to dive in and fully understand something, inside and out. Even if no one ever reads what you write, the process of doing it is more than worth it.

Be sure to read the full article here: