Ask HN: Strategies for not screwing up?

Yesterday I was trying to update a status flag on a couple MySQL records. I've learned to always select the dataset first to make sure the correct records are going to be updated. When writing the SQL update I copied and pasted the WHERE part of the select and ran the command. It errored out and so a quick review made it look like I had missed an AND. So the SQL looked something like this: UPDATE table SET flag = 1 AND m = 123 AND s = 888 which updated nearly 5 years worth of data and 100K records by nuking the actual flag value. I was able to essentially restore the flag from a backup but it got me thinking about strategies to prevent oneself from being your own worst enemy. Doesn't have to be SQL related. Thanks!