In both questions and answers…
I find that it is oftentimes that I am hacking away, writing an answer only to realize that a silly mistake I made quite some lines above has done me in and I have to go back and redo a significant chunk. This wastes quite a bit of time.
Even worse is when I have hacked away at a problem and submitted it, only to realize some time later that there’s a fatal error in the body… and a whole mess ensues. This wastes my time and the time of people who end up reading it before I realize.
In fact, how can one avoid silly mistakes in general?
In time-based competitive examinations, candidates do not always have enough time to mull over what they have just done and fix mistakes. Not only that, a silly mistake in such a high stress, often high stakes situation is even more likely. And for those prone to making such errors, the stress of looking out particularly for silly mistakes while solving wastes a lot of time.
Silly mistakes range from a missed sign ($\pm$), to a botched expansion, to mixing up coefficients, to falling to abuse of notation, to simply having misread the question… simply put, any petty but fatal error that you commit despite clearly knowing better. (Or, maybe understanding better is a more accurate expression).
Looking forward to responses.