Premature optimisation, in programming, is the act of optimising a piece of code before we know that we need to. It's an important problem to spot because it's often a waste of time; there are other tasks to do and what appears to be a problem at the micro level might only be a fraction of the entire system. You can't tell what's important without taking a step back to analyse the whole.
When you're deciding what to do in a more general sense it's important to take this same birds-eye view. Focus on the goals that matter in the long run, and come back to the less important issues if you have time.
There are a lot of tips out there claiming to make you more productive & increase your efficiency. Make sure you're not prematurely optimising.